Turn on sized_box_for_whitespace lint, fix instances. (#77099)

analysis_options.yaml

@@ -181,7 +181,7 @@ linter:
     - provide_deprecation_message
     # - public_member_api_docs # enabled on a case-by-case basis; see e.g. packages/analysis_options.yaml
     - recursive_getters
-    # - sized_box_for_whitespace # not yet tested
+    - sized_box_for_whitespace
     - slash_for_doc_comments
     # - sort_child_properties_last # not yet tested
     - sort_constructors_first

dev/automated_tests/flutter_test/print_correct_local_widget_test.dart

@@ -14,7 +14,7 @@ void main() {
           appBar: AppBar(
             title: const Text('RenderFlex OverFlow'),
           ),
-          body: Container(
+          body: SizedBox(
             width: 400.0,
             child: Row(
               children: <Widget>[

dev/benchmarks/macrobenchmarks/lib/src/simple_scroll.dart

@@ -12,7 +12,7 @@ class SimpleScroll extends StatelessWidget {
     return ListView(
       children: <Widget>[
         for (int n = 0; n < 200; n += 1)
-          Container(height: 40.0, child: Text('$n')),
+          SizedBox(height: 40.0, child: Text('$n')),
       ],
     );
   }

dev/benchmarks/macrobenchmarks/lib/src/stack_size.dart

@@ -87,11 +87,11 @@ class StackSizePage extends StatelessWidget {
   Widget build(BuildContext context) {
     return Material(
       child: Column(
-        children: <Widget>[
-          Container(
+        children: const <Widget>[
+          SizedBox(
             width: 200,
             height: 100,
-            child: const ParentWidget(),
+            child: ParentWidget(),
           ),
         ],
       ),

dev/benchmarks/macrobenchmarks/lib/src/text.dart

@@ -11,11 +11,11 @@ class TextPage extends StatelessWidget {
   Widget build(BuildContext context) {
     return Material(
       child: Column(
-        children: <Widget>[
-          Container(
+        children: const <Widget>[
+          SizedBox(
             width: 200,
             height: 100,
-            child: const TextField(
+            child: TextField(
               key: Key('basic-textfield'),
             ),
           ),

dev/integration_tests/external_ui/lib/main.dart

@@ -136,10 +136,10 @@ Press play to produce texture frames.''';
           child: Column(
             mainAxisAlignment: MainAxisAlignment.center,
             children: <Widget>[
-              Container(
+              const SizedBox(
                 width: 300.0,
                 height: 200.0,
-                child: const Texture(textureId: 0),
+                child: Texture(textureId: 0),
               ),
               Container(
                 width: 300.0,

dev/integration_tests/flutter_gallery/lib/demo/cupertino/cupertino_refresh_demo.dart

@@ -164,7 +164,7 @@ class _ListItem extends StatelessWidget {
       padding: const EdgeInsets.only(top: 9.0),
       child: Row(
         children: <Widget>[
-          Container(
+          SizedBox(
             width: 38.0,
             child: called!
                 ? Align(

dev/integration_tests/flutter_gallery/lib/demo/material/bottom_app_bar_demo.dart

@@ -433,7 +433,7 @@ class _DiamondFab extends StatelessWidget {
       color: Colors.orange,
       child: InkWell(
         onTap: onPressed,
-        child: Container(
+        child: SizedBox(
           width: 56.0,
           height: 56.0,
           child: IconTheme.merge(

dev/integration_tests/flutter_gallery/lib/demo/material/reorderable_list_demo.dart

@@ -146,7 +146,7 @@ class _ListDemoState extends State<ReorderableListDemo> {
         break;
       case _ReorderableListType.horizontalAvatar:
       case _ReorderableListType.verticalAvatar:
-        listTile = Container(
+        listTile = SizedBox(
           key: Key(item.value),
           height: 100.0,
           width: 100.0,

dev/integration_tests/flutter_gallery/lib/demo/shrine/expanding_bottom_sheet.dart

@@ -324,7 +324,7 @@ class _ExpandingBottomSheetState extends State<ExpandingBottomSheet> with Ticker
     return Semantics(
       button: true,
       value: 'Shopping cart, $totalCartQuantity items',
-      child: Container(
+      child: SizedBox(
         width: _widthAnimation.value,
         height: _heightAnimation.value,
         child: Material(

dev/integration_tests/flutter_gallery/lib/demo/shrine/supplemental/asymmetric_view.dart

@@ -12,9 +12,9 @@ class AsymmetricView extends StatelessWidget {
 
   final List<Product>? products;
 
-  List<Container> _buildColumns(BuildContext context) {
+  List<SizedBox> _buildColumns(BuildContext context) {
     if (products == null || products!.isEmpty) {
-      return const <Container>[];
+      return const <SizedBox>[];
     }
 
     // This will return a list of columns. It will oscillate between the two
@@ -25,7 +25,7 @@ class AsymmetricView extends StatelessWidget {
     // some kinda awkward math so we use _evenCasesIndex and _oddCasesIndex as
     // helpers for creating the index of the product list that will correspond
     // to the index of the list of columns.
-    return List<Container>.generate(_listItemCount(products!.length), (int index) {
+    return List<SizedBox>.generate(_listItemCount(products!.length), (int index) {
       double width = .59 * MediaQuery.of(context).size.width;
       Widget column;
       if (index.isEven) {
@@ -44,7 +44,7 @@ class AsymmetricView extends StatelessWidget {
           product: products![_oddCasesIndex(index)],
         );
       }
-      return Container(
+      return SizedBox(
         width: width,
         child: Padding(
           padding: const EdgeInsets.symmetric(horizontal: 16.0),

dev/integration_tests/flutter_gallery/lib/demo/transformations/transformations_demo_gesture_transformable.dart

@@ -286,7 +286,7 @@ class _GestureTransformableState extends State<GestureTransformable> with Ticker
         // The scene is panned/zoomed/rotated using this Transform widget.
         child: Transform(
           transform: _transform,
-          child: Container(
+          child: SizedBox(
             child: widget.child,
             height: widget.size.height,
             width: widget.size.width,

dev/integration_tests/flutter_gallery/test_memory/image_cache_memory.dart

@@ -20,7 +20,7 @@ Future<void> main() async {
       key: const Key('ImageList'),
       itemCount: numItems,
       itemBuilder: (BuildContext context, int position) {
-        return Container(
+        return SizedBox(
           width: 200,
           height: 200,
           child: Center(

dev/integration_tests/ios_platform_view_tests/lib/main.dart

@@ -81,9 +81,9 @@ class PlatformViewPage extends StatelessWidget {
       ),
       body: Column(
         children: <Widget>[
-          Expanded(
-            child: Container(
-              child: const UiKitView(viewType: 'platform_view'),
+          const Expanded(
+            child: SizedBox(
+              child: UiKitView(viewType: 'platform_view'),
               width: 300,
             ),
           ),

dev/manual_tests/lib/drag_and_drop.dart

@@ -198,10 +198,10 @@ class MovableBall extends StatelessWidget {
         child: const Center(child: Text('BALL')),
       ),
     );
-    final Widget dashedBall = Container(
+    const Widget dashedBall = SizedBox(
       width: kBallSize,
       height: kBallSize,
-      child: const CustomPaint(
+      child: CustomPaint(
         painter: DashOutlineCirclePainter()
       ),
     );

examples/layers/widgets/spinning_mixed.dart

@@ -38,7 +38,7 @@ void attachWidgetTreeToRenderTree(RenderProxyBox container) {
     container: container,
     child: Directionality(
       textDirection: TextDirection.ltr,
-      child: Container(
+      child: SizedBox(
         height: 300.0,
         child: Column(
           children: <Widget>[

packages/flutter/lib/src/material/autocomplete.dart

@@ -228,7 +228,7 @@ class _AutocompleteOptions<T extends Object> extends StatelessWidget {
       alignment: Alignment.topLeft,
       child: Material(
         elevation: 4.0,
-        child: Container(
+        child: SizedBox(
           height: 200.0,
           child: ListView.builder(
             padding: EdgeInsets.zero,

packages/flutter/lib/src/material/calendar_date_picker.dart

@@ -383,7 +383,7 @@ class _DatePickerModeToggleButtonState extends State<_DatePickerModeToggleButton
               label: MaterialLocalizations.of(context).selectYearSemanticsLabel,
               excludeSemantics: true,
               button: true,
-              child: Container(
+              child: SizedBox(
                 height: _subHeaderHeight,
                 child: InkWell(
                   onTap: widget.onTitlePressed,

packages/flutter/lib/src/material/date_picker_deprecated.dart

@@ -314,7 +314,7 @@ class DayPicker extends StatelessWidget {
       padding: const EdgeInsets.symmetric(horizontal: 8.0),
       child: Column(
         children: <Widget>[
-          Container(
+          SizedBox(
             height: _kDayPickerRowHeight,
             child: Center(
               child: ExcludeSemantics(

packages/flutter/lib/src/material/paginated_data_table.dart

@@ -539,7 +539,7 @@ class PaginatedDataTableState extends State<PaginatedDataTable> {
                   data: const IconThemeData(
                     opacity: 0.54
                   ),
-                  child: Container(
+                  child: SizedBox(
                     // TODO(bkonyi): this won't handle text zoom correctly,
                     //  https://github.com/flutter/flutter/issues/48522
                     height: 56.0,

packages/flutter/lib/src/material/stepper.dart

@@ -682,7 +682,7 @@ class _StepperState extends State<Stepper> with TickerProviderStateMixin {
           canRequestFocus: widget.steps[i].state != StepState.disabled,
           child: Row(
             children: <Widget>[
-              Container(
+              SizedBox(
                 height: 72.0,
                 child: Center(
                   child: _buildIcon(i),

packages/flutter/lib/src/material/time_picker.dart

@@ -159,7 +159,7 @@ class _TimePickerHeader extends StatelessWidget {
         controls = Column(
           children: <Widget>[
             const SizedBox(height: 16.0),
-            Container(
+            SizedBox(
               height: kMinInteractiveDimension * 2,
               child: Row(
                 children: <Widget>[
@@ -209,7 +209,7 @@ class _TimePickerHeader extends StatelessWidget {
                   orientation: orientation,
                   onChanged: onChanged,
                 ),
-              Container(
+              SizedBox(
                 height: kMinInteractiveDimension * 2,
                 child: Row(
                   // Hour/minutes should not change positions in RTL locales.
@@ -287,7 +287,7 @@ class _HourMinuteControl extends StatelessWidget {
     final ShapeBorder shape = timePickerTheme.hourMinuteShape ?? _kDefaultShape;
 
     final Set<MaterialState> states = isSelected ? <MaterialState>{MaterialState.selected} : <MaterialState>{};
-    return Container(
+    return SizedBox(
       height: _kTimePickerHeaderControlHeight,
       child: Material(
         color: MaterialStateProperty.resolveAs(backgroundColor, states),
@@ -610,7 +610,7 @@ class _DayPeriodControl extends StatelessWidget {
         result = _DayPeriodInputPadding(
           minSize: const Size(width, kMinInteractiveDimension * 2),
           orientation: orientation,
-          child: Container(
+          child: SizedBox(
             width: width,
             height: _kTimePickerHeaderControlHeight,
             child: Material(
@@ -637,7 +637,7 @@ class _DayPeriodControl extends StatelessWidget {
         result = _DayPeriodInputPadding(
           minSize: const Size(0.0, kMinInteractiveDimension),
           orientation: orientation,
-          child: Container(
+          child: SizedBox(
             height: 40.0,
             child: Material(
               clipBehavior: Clip.antiAlias,

packages/flutter/lib/src/services/platform_channel.dart

@@ -292,7 +292,7 @@ class MethodChannel {
   ///     NSArray* items = [BWPlayApi items];
   ///     NSMutableArray* json = [NSMutableArray arrayWithCapacity:items.count];
   ///     for (final BWPlayItem* item in items) {
-  ///       [json addObject:@{@"id":item.itemId, @"title":item.name, @"artist":item.artist}];
+  ///       [json addObject:@{ @"id":item.itemId, @"title":item.name, @"artist":item.artist }];
   ///     }
   ///     result(json);
   ///   } else if ([@"play" isEqualToString:call.method]) {

packages/flutter/test/cupertino/date_picker_test.dart

@@ -1502,7 +1502,7 @@ Widget _buildPicker({
       onSelectedItemChanged: onSelectedItemChanged,
       children: List<Widget>.generate(100, (int index) {
         return Center(
-          child: Container(
+          child: SizedBox(
             width: 400.0,
             height: 100.0,
             child: Text(index.toString()),

packages/flutter/test/cupertino/picker_test.dart

@@ -22,7 +22,7 @@ void main() {
               itemExtent: 50.0,
               onSelectedItemChanged: (_) { },
               children: List<Widget>.generate(3, (int index) {
-                return Container(
+                return SizedBox(
                   height: 50.0,
                   width: 300.0,
                   child: Text(index.toString()),
@@ -65,7 +65,7 @@ void main() {
                 itemExtent: 50.0,
                 onSelectedItemChanged: (_) { },
                 children: List<Widget>.generate(3, (int index) {
-                  return Container(
+                  return SizedBox(
                     height: 50.0,
                     width: 300.0,
                     child: Text(index.toString()),
@@ -78,7 +78,7 @@ void main() {
       );
 
       expect(
-        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        tester.getTopLeft(find.widgetWithText(SizedBox, '1').first),
         const Offset(0.0, 125.0),
       );
 
@@ -86,11 +86,11 @@ void main() {
       await tester.pump();
 
       expect(
-        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        tester.getTopLeft(find.widgetWithText(SizedBox, '1').first),
         const Offset(0.0, 175.0),
       );
       expect(
-        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        tester.getTopLeft(find.widgetWithText(SizedBox, '0').first),
         const Offset(0.0, 125.0),
       );
     });
@@ -191,7 +191,7 @@ void main() {
               onSelectedItemChanged: (int index) { selectedItems.add(index); },
               children: List<Widget>.generate(100, (int index) {
                 return Center(
-                  child: Container(
+                  child: SizedBox(
                     width: 400.0,
                     height: 100.0,
                     child: Text(index.toString()),
@@ -242,7 +242,7 @@ void main() {
               onSelectedItemChanged: (int index) { selectedItems.add(index); },
               children: List<Widget>.generate(100, (int index) {
                 return Center(
-                  child: Container(
+                  child: SizedBox(
                     width: 400.0,
                     height: 100.0,
                     child: Text(index.toString()),
@@ -272,7 +272,7 @@ void main() {
             onSelectedItemChanged: (int index) { selectedItems.add(index); },
             children: List<Widget>.generate(100, (int index) {
               return Center(
-                child: Container(
+                child: SizedBox(
                   width: 400.0,
                   height: 100.0,
                   child: Text(index.toString()),
@@ -288,14 +288,14 @@ void main() {
 
       // The item that was in the center now moved a bit.
       expect(
-        tester.getTopLeft(find.widgetWithText(Container, '10')),
+        tester.getTopLeft(find.widgetWithText(SizedBox, '10')),
         const Offset(200.0, 280.0),
       );
 
       await tester.pumpAndSettle();
 
       expect(
-        tester.getTopLeft(find.widgetWithText(Container, '10')).dy,
+        tester.getTopLeft(find.widgetWithText(SizedBox, '10')).dy,
         moreOrLessEquals(250.0, epsilon: 0.5),
       );
       expect(selectedItems.isEmpty, true);
@@ -306,7 +306,7 @@ void main() {
       await tester.pumpAndSettle();
 
       expect(
-        tester.getTopLeft(find.widgetWithText(Container, '10')).dy,
+        tester.getTopLeft(find.widgetWithText(SizedBox, '10')).dy,
         // It's down by 100.0 now.
         moreOrLessEquals(350.0, epsilon: 0.5),
       );
@@ -327,7 +327,7 @@ void main() {
             onSelectedItemChanged: (int index) { selectedItems.add(index); },
             children: List<Widget>.generate(100, (int index) {
               return Center(
-                child: Container(
+                child: SizedBox(
                   width: 400.0,
                   height: 100.0,
                   child: Text(index.toString()),
@@ -348,7 +348,7 @@ void main() {
 
       // Should have been flung far enough that even the first item goes off
       // screen and gets removed.
-      expect(find.widgetWithText(Container, '0').evaluate().isEmpty, true);
+      expect(find.widgetWithText(SizedBox, '0').evaluate().isEmpty, true);
 
       expect(
         selectedItems,
@@ -361,7 +361,7 @@ void main() {
       await tester.pumpAndSettle();
 
       expect(
-        tester.getTopLeft(find.widgetWithText(Container, '0')).dy,
+        tester.getTopLeft(find.widgetWithText(SizedBox, '0')).dy,
         // Should have sprung back to the middle now.
         moreOrLessEquals(250.0),
       );

packages/flutter/test/cupertino/refresh_test.dart

@@ -21,7 +21,7 @@ void main() {
     return SliverList(
       delegate: SliverChildBuilderDelegate(
         (BuildContext context, int index) {
-          return Container(
+          return SizedBox(
             height: 200.0,
             child: Center(child: Text(index.toString())),
           );
@@ -50,7 +50,7 @@ void main() {
       expect(mockHelper.invocations, isEmpty);
 
       expect(
-        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        tester.getTopLeft(find.widgetWithText(SizedBox, '0')),
         Offset.zero,
       );
     }, variant: const TargetPlatformVariant(<TargetPlatform>{ TargetPlatform.iOS,  TargetPlatform.macOS }));
@@ -85,7 +85,7 @@ void main() {
       expect(mockHelper.invocations, hasLength(1));
 
       expect(
-        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        tester.getTopLeft(find.widgetWithText(SizedBox, '0')),
         const Offset(0.0, 50.0),
       );
     }, variant: const TargetPlatformVariant(<TargetPlatform>{ TargetPlatform.iOS,  TargetPlatform.macOS }));
@@ -114,7 +114,7 @@ void main() {
         expect(mockHelper.invocations, isEmpty);
 
         expect(
-          tester.getTopLeft(find.widgetWithText(Container, '0')),
+          tester.getTopLeft(find.widgetWithText(SizedBox, '0')),
           Offset.zero,
         );
     }, variant: TargetPlatformVariant.only(TargetPlatform.android));
@@ -165,7 +165,7 @@ void main() {
       expect(mockHelper.invocations, hasLength(3));
 
       expect(
-        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        tester.getTopLeft(find.widgetWithText(SizedBox, '0')),
         Offset.zero,
       );
     }, variant: const TargetPlatformVariant(<TargetPlatform>{ TargetPlatform.iOS,  TargetPlatform.macOS }));
@@ -282,7 +282,7 @@ void main() {
         // Stays in that state forever until future completes.
         await tester.pump(const Duration(seconds: 1000));
         expect(
-          tester.getTopLeft(find.widgetWithText(Container, '0')),
+          tester.getTopLeft(find.widgetWithText(SizedBox, '0')),
           const Offset(0.0, 60.0),
         );
 
@@ -355,7 +355,7 @@ void main() {
             // Stays in that state forever until future completes.
             await tester.pump(const Duration(seconds: 1000));
             expect(
-              tester.getTopLeft(find.widgetWithText(Container, '0')),
+              tester.getTopLeft(find.widgetWithText(SizedBox, '0')),
               const Offset(0.0, 60.0),
             );
 
@@ -840,8 +840,8 @@ void main() {
           ),
         );
 
-        await tester.fling(find.byType(Container).first, const Offset(0.0, 200.0), 2000.0);
-        await tester.fling(find.byType(Container).first, const Offset(0.0, -200.0), 3000.0, warnIfMissed: false); // IgnorePointer is enabled while scroll is ballistic.
+        await tester.fling(find.byType(SizedBox).first, const Offset(0.0, 200.0), 2000.0);
+        await tester.fling(find.byType(SizedBox).first, const Offset(0.0, -200.0), 3000.0, warnIfMissed: false); // IgnorePointer is enabled while scroll is ballistic.
 
         expect(mockHelper.invocations, isEmpty);
     }, variant: const TargetPlatformVariant(<TargetPlatform>{ TargetPlatform.iOS,  TargetPlatform.macOS }));
@@ -937,7 +937,7 @@ void main() {
         ),
       );
 
-      final double initialFirstCellY = tester.getTopLeft(find.widgetWithText(Container, '0')).dy;
+      final double initialFirstCellY = tester.getTopLeft(find.widgetWithText(SizedBox, '0')).dy;
 
       // Drag down but not enough to trigger the refresh.
       await tester.drag(find.text('0'), const Offset(0.0, 50.0), touchSlopY: 0);
@@ -952,7 +952,7 @@ void main() {
       expect(mockHelper.invocations, hasLength(1));
 
       expect(
-        tester.getTopLeft(find.widgetWithText(Container, '0')).dy,
+        tester.getTopLeft(find.widgetWithText(SizedBox, '0')).dy,
         initialFirstCellY + 50
       );
     }, variant: const TargetPlatformVariant(<TargetPlatform>{ TargetPlatform.iOS,  TargetPlatform.macOS }));
@@ -1074,7 +1074,7 @@ void main() {
         await gesture.moveBy(const Offset(0.0, -80.0)); // Overscrolling, need to move more than -40.
         await tester.pump();
         expect(
-          tester.getTopLeft(find.widgetWithText(Container, '0')).dy,
+          tester.getTopLeft(find.widgetWithText(SizedBox, '0')).dy,
           moreOrLessEquals(49.775111111111116), // Below 50 now.
         );
         expect(
@@ -1116,7 +1116,7 @@ void main() {
           RefreshIndicatorMode.refresh,
         );
         expect(
-          tester.getRect(find.widgetWithText(Container, '0')),
+          tester.getRect(find.widgetWithText(SizedBox, '0')),
           const Rect.fromLTRB(0.0, 60.0, 800.0, 260.0),
         );
 
@@ -1167,7 +1167,7 @@ void main() {
         await gesture.moveBy(const Offset(0.0, -200.0));
         await tester.pump();
         expect(
-          tester.getTopLeft(find.widgetWithText(Container, '0')).dy,
+          tester.getTopLeft(find.widgetWithText(SizedBox, '0')).dy,
           moreOrLessEquals(27.944444444444457),
         );
         // Need to bring it to 100 * 0.1 to reset to inactive.
@@ -1179,7 +1179,7 @@ void main() {
         await gesture.moveBy(const Offset(0.0, -35.0));
         await tester.pump();
         expect(
-          tester.getTopLeft(find.widgetWithText(Container, '0')).dy,
+          tester.getTopLeft(find.widgetWithText(SizedBox, '0')).dy,
           moreOrLessEquals(9.313890708161875),
         );
         expect(
@@ -1219,7 +1219,7 @@ void main() {
         await tester.pump();
         // The refresh indicator is offscreen now.
         expect(
-          tester.getTopLeft(find.widgetWithText(Container, '0')).dy,
+          tester.getTopLeft(find.widgetWithText(SizedBox, '0')).dy,
           moreOrLessEquals(-145.0332383665717),
         );
         expect(
@@ -1236,13 +1236,13 @@ void main() {
         );
         // Nothing moved.
         expect(
-          tester.getTopLeft(find.widgetWithText(Container, '0')).dy,
+          tester.getTopLeft(find.widgetWithText(SizedBox, '0')).dy,
           moreOrLessEquals(-145.0332383665717),
         );
         await tester.pump(const Duration(seconds: 2));
         // Everything stayed as is.
         expect(
-          tester.getTopLeft(find.widgetWithText(Container, '0')).dy,
+          tester.getTopLeft(find.widgetWithText(SizedBox, '0')).dy,
           moreOrLessEquals(-145.0332383665717),
         );
     }, variant: const TargetPlatformVariant(<TargetPlatform>{ TargetPlatform.iOS,  TargetPlatform.macOS }));

packages/flutter/test/cupertino/route_test.dart

@@ -1118,7 +1118,7 @@ void main() {
               child: Hero(
                 tag: 'tag',
                 transitionOnUserGestures: true,
-                child: Container(key: container, height: 150.0, width: 150.0)
+                child: SizedBox(key: container, height: 150.0, width: 150.0)
               ),
             )
           );
@@ -1131,7 +1131,7 @@ void main() {
                 child: Hero(
                   tag: 'tag',
                   transitionOnUserGestures: true,
-                  child: Container(key: container, height: 150.0, width: 150.0)
+                  child: SizedBox(key: container, height: 150.0, width: 150.0)
                 )
               ),
             )

packages/flutter/test/cupertino/text_field_test.dart

@@ -4217,7 +4217,7 @@ void main() {
             mainAxisAlignment: MainAxisAlignment.center,
             mainAxisSize: MainAxisSize.min,
             children: <Widget>[
-              Container(
+              SizedBox(
                 width: 100.0,
                 child: CupertinoTextField(
                   controller: controller1,
@@ -4228,21 +4228,21 @@ void main() {
                 mainAxisAlignment: MainAxisAlignment.center,
                 mainAxisSize: MainAxisSize.min,
                 children: <Widget>[
-                  Container(
+                  SizedBox(
                     width: 100.0,
                     child: CupertinoTextField(
                       controller: controller2,
                       focusNode: focusNode2,
                     ),
                   ),
-                  Container(
+                  SizedBox(
                     width: 100.0,
                     child: CupertinoTextField(
                       controller: controller3,
                       focusNode: focusNode3,
                     ),
                   ),
-                  Container(
+                  SizedBox(
                     width: 100.0,
                     child: CupertinoTextField(
                       controller: controller4,
@@ -4251,7 +4251,7 @@ void main() {
                   ),
                 ],
               ),
-              Container(
+              SizedBox(
                 width: 100.0,
                 child: CupertinoTextField(
                   controller: controller5,

packages/flutter/test/cupertino/text_selection_toolbar_test.dart

@@ -54,6 +54,13 @@ class _CustomCupertinoTextSelectionControls extends CupertinoTextSelectionContro
   }
 }
 
+class TestBox extends SizedBox {
+  const TestBox({Key? key}) : super(key: key, width: itemWidth, height: itemHeight);
+
+  static const double itemHeight = 44.0;
+  static const double itemWidth = 100.0;
+}
+
 void main() {
   TestWidgetsFlutterBinding.ensureInitialized();
 
@@ -75,18 +82,7 @@ void main() {
 
   testWidgets('paginates children if they overflow', (WidgetTester tester) async {
     late StateSetter setState;
-    const double height = 44.0;
-    const double itemWidth = 100.0;
-    final List<Widget> children = <Widget>[
-      Container(width: itemWidth, height: height),
-      Container(width: itemWidth, height: height),
-      Container(width: itemWidth, height: height),
-      Container(width: itemWidth, height: height),
-      Container(width: itemWidth, height: height),
-      Container(width: itemWidth, height: height),
-      Container(width: itemWidth, height: height),
-    ];
-
+    final List<Widget> children = List<Widget>.generate(7, (int i) => const TestBox());
     await tester.pumpWidget(
       CupertinoApp(
         home: Center(
@@ -105,25 +101,25 @@ void main() {
     );
 
     // All children fit on the screen, so they are all rendered.
-    expect(find.byType(Container), findsNWidgets(children.length));
+    expect(find.byType(TestBox), findsNWidgets(children.length));
     expect(_findOverflowNextButton(), findsNothing);
     expect(_findOverflowBackButton(), findsNothing);
 
     // Adding one more child makes the children overflow.
     setState(() {
       children.add(
-        Container(width: itemWidth, height: height),
+        const TestBox(),
       );
     });
     await tester.pumpAndSettle();
-    expect(find.byType(Container), findsNWidgets(children.length - 1));
+    expect(find.byType(TestBox), findsNWidgets(children.length - 1));
     expect(_findOverflowNextButton(), findsOneWidget);
     expect(_findOverflowBackButton(), findsNothing);
 
     // Tap the overflow next button to show the next page of children.
     await tester.tap(_findOverflowNextButton());
     await tester.pumpAndSettle();
-    expect(find.byType(Container), findsNWidgets(1));
+    expect(find.byType(TestBox), findsNWidgets(1));
     expect(_findOverflowNextButton(), findsOneWidget);
     expect(_findOverflowBackButton(), findsOneWidget);
 
@@ -131,28 +127,28 @@ void main() {
     // disabled and there are no more children to display.
     await tester.tap(_findOverflowNextButton());
     await tester.pumpAndSettle();
-    expect(find.byType(Container), findsNWidgets(1));
+    expect(find.byType(TestBox), findsNWidgets(1));
     expect(_findOverflowNextButton(), findsOneWidget);
     expect(_findOverflowBackButton(), findsOneWidget);
 
     // Tap the overflow back button to go back to the first page.
     await tester.tap(_findOverflowBackButton());
     await tester.pumpAndSettle();
-    expect(find.byType(Container), findsNWidgets(7));
+    expect(find.byType(TestBox), findsNWidgets(7));
     expect(_findOverflowNextButton(), findsOneWidget);
     expect(_findOverflowBackButton(), findsNothing);
 
     // Adding 7 more children overflows onto a third page.
     setState(() {
-      children.add(Container(width: itemWidth, height: height));
-      children.add(Container(width: itemWidth, height: height));
-      children.add(Container(width: itemWidth, height: height));
-      children.add(Container(width: itemWidth, height: height));
-      children.add(Container(width: itemWidth, height: height));
-      children.add(Container(width: itemWidth, height: height));
+      children.add(const TestBox());
+      children.add(const TestBox());
+      children.add(const TestBox());
+      children.add(const TestBox());
+      children.add(const TestBox());
+      children.add(const TestBox());
     });
     await tester.pumpAndSettle();
-    expect(find.byType(Container), findsNWidgets(7));
+    expect(find.byType(TestBox), findsNWidgets(7));
     expect(_findOverflowNextButton(), findsOneWidget);
     expect(_findOverflowBackButton(), findsNothing);
 
@@ -160,28 +156,28 @@ void main() {
     await tester.tap(_findOverflowNextButton());
     await tester.pumpAndSettle();
     // With the back button, only six children fit on this page.
-    expect(find.byType(Container), findsNWidgets(6));
+    expect(find.byType(TestBox), findsNWidgets(6));
     expect(_findOverflowNextButton(), findsOneWidget);
     expect(_findOverflowBackButton(), findsOneWidget);
 
     // Tap the overflow next button again to show the third page of children.
     await tester.tap(_findOverflowNextButton());
     await tester.pumpAndSettle();
-    expect(find.byType(Container), findsNWidgets(1));
+    expect(find.byType(TestBox), findsNWidgets(1));
     expect(_findOverflowNextButton(), findsOneWidget);
     expect(_findOverflowBackButton(), findsOneWidget);
 
     // Tap the overflow back button to go back to the second page.
     await tester.tap(_findOverflowBackButton());
     await tester.pumpAndSettle();
-    expect(find.byType(Container), findsNWidgets(6));
+    expect(find.byType(TestBox), findsNWidgets(6));
     expect(_findOverflowNextButton(), findsOneWidget);
     expect(_findOverflowBackButton(), findsOneWidget);
 
     // Tap the overflow back button to go back to the first page.
     await tester.tap(_findOverflowBackButton());
     await tester.pumpAndSettle();
-    expect(find.byType(Container), findsNWidgets(7));
+    expect(find.byType(TestBox), findsNWidgets(7));
     expect(_findOverflowNextButton(), findsOneWidget);
     expect(_findOverflowBackButton(), findsNothing);
   }, skip: kIsWeb);

packages/flutter/test/material/app_bar_test.dart

@@ -487,7 +487,7 @@ void main() {
     await tester.pumpWidget(
       MaterialApp(
         home: Center(
-          child: Container(
+          child: SizedBox(
             height: 0.0,
             width: 0.0,
             child: Scaffold(

packages/flutter/test/material/bottom_sheet_test.dart

@@ -750,7 +750,7 @@ void main() {
                 );
               },
               behavior: HitTestBehavior.opaque,
-              child: Container(
+              child: const SizedBox(
                 height: 100.0,
                 width: 100.0,
               ),
@@ -802,18 +802,16 @@ void main() {
                     reverseDuration: const Duration(seconds: 2),
                   ),
                   builder: (BuildContext context) {
-                    return Container(
-                      child: MaterialButton(
-                        child: const Text('BottomSheet'),
-                        onPressed: () => Navigator.pop(context),
-                        key: tapTargetToClose,
-                      ),
+                    return MaterialButton(
+                      child: const Text('BottomSheet'),
+                      onPressed: () => Navigator.pop(context),
+                      key: tapTargetToClose,
                     );
                   },
                 );
               },
               behavior: HitTestBehavior.opaque,
-              child: Container(
+              child: const SizedBox(
                 height: 100.0,
                 width: 100.0,
               ),

packages/flutter/test/material/button_bar_test.dart

@@ -90,16 +90,16 @@ void main() {
       const Key child2Key = Key('child2');
 
       await tester.pumpWidget(
-        MaterialApp(
+        const MaterialApp(
           home: Center(
             child: ButtonBar(
               key: buttonBarKey,
               // buttonPadding set to zero to simplify test calculations.
               buttonPadding: EdgeInsets.zero,
               children: <Widget>[
-                Container(key: child0Key, width: 100.0, height: 100.0),
-                Container(key: child1Key, width: 100.0, height: 100.0),
-                Container(key: child2Key, width: 100.0, height: 100.0),
+                SizedBox(key: child0Key, width: 100.0, height: 100.0),
+                SizedBox(key: child1Key, width: 100.0, height: 100.0),
+                SizedBox(key: child2Key, width: 100.0, height: 100.0),
               ],
             ),
           ),
@@ -136,9 +136,9 @@ void main() {
       const Key child1Key = Key('child1');
       const Key child2Key = Key('child2');
       await tester.pumpWidget(
-        MaterialApp(
+        const MaterialApp(
           home: ButtonBarTheme(
-            data: const ButtonBarThemeData(
+            data: ButtonBarThemeData(
               mainAxisSize: MainAxisSize.min,
             ),
             child: Center(
@@ -147,9 +147,9 @@ void main() {
                 // buttonPadding set to zero to simplify test calculations.
                 buttonPadding: EdgeInsets.zero,
                 children: <Widget>[
-                  Container(key: child0Key, width: 100.0, height: 100.0),
-                  Container(key: child1Key, width: 100.0, height: 100.0),
-                  Container(key: child2Key, width: 100.0, height: 100.0),
+                  SizedBox(key: child0Key, width: 100.0, height: 100.0),
+                  SizedBox(key: child1Key, width: 100.0, height: 100.0),
+                  SizedBox(key: child2Key, width: 100.0, height: 100.0),
                 ],
               ),
             ),
@@ -191,9 +191,9 @@ void main() {
       const Key child1Key = Key('child1');
       const Key child2Key = Key('child2');
       await tester.pumpWidget(
-        MaterialApp(
+        const MaterialApp(
           home: ButtonBarTheme(
-            data: const ButtonBarThemeData(
+            data: ButtonBarThemeData(
               mainAxisSize: MainAxisSize.min,
             ),
             child: Center(
@@ -203,9 +203,9 @@ void main() {
                 buttonPadding: EdgeInsets.zero,
                 mainAxisSize: MainAxisSize.max,
                 children: <Widget>[
-                  Container(key: child0Key, width: 100.0, height: 100.0),
-                  Container(key: child1Key, width: 100.0, height: 100.0),
-                  Container(key: child2Key, width: 100.0, height: 100.0),
+                  SizedBox(key: child0Key, width: 100.0, height: 100.0),
+                  SizedBox(key: child1Key, width: 100.0, height: 100.0),
+                  SizedBox(key: child2Key, width: 100.0, height: 100.0),
                 ],
               ),
             ),
@@ -394,8 +394,8 @@ void main() {
         MaterialApp(
           home: ButtonBar(
             children: <Widget>[
-              Container(key: keyOne, height: 50.0, width: 800.0),
-              Container(key: keyTwo, height: 50.0, width: 800.0),
+              SizedBox(key: keyOne, height: 50.0, width: 800.0),
+              SizedBox(key: keyTwo, height: 50.0, width: 800.0),
             ],
           ),
         ),
@@ -419,8 +419,8 @@ void main() {
               // Set padding to zero to align buttons with edge of button bar.
               buttonPadding: EdgeInsets.zero,
               children: <Widget>[
-                Container(key: keyOne, height: 50.0, width: 500.0),
-                Container(key: keyTwo, height: 50.0, width: 500.0),
+                SizedBox(key: keyOne, height: 50.0, width: 500.0),
+                SizedBox(key: keyTwo, height: 50.0, width: 500.0),
               ],
             ),
           ),
@@ -447,8 +447,8 @@ void main() {
             // Set padding to zero to align buttons with edge of button bar.
             buttonPadding: EdgeInsets.zero,
             children: <Widget>[
-              Container(key: keyOne, height: 50.0, width: 500.0),
-              Container(key: keyTwo, height: 50.0, width: 500.0),
+              SizedBox(key: keyOne, height: 50.0, width: 500.0),
+              SizedBox(key: keyTwo, height: 50.0, width: 500.0),
             ],
           ),
         ),
@@ -474,8 +474,8 @@ void main() {
             // Set padding to zero to align buttons with edge of button bar.
             buttonPadding: EdgeInsets.zero,
             children: <Widget>[
-              Container(key: keyOne, height: 50.0, width: 500.0),
-              Container(key: keyTwo, height: 50.0, width: 500.0),
+              SizedBox(key: keyOne, height: 50.0, width: 500.0),
+              SizedBox(key: keyTwo, height: 50.0, width: 500.0),
             ],
           ),
         ),
@@ -504,8 +504,8 @@ void main() {
               // Set padding to zero to align buttons with edge of button bar.
               buttonPadding: EdgeInsets.zero,
               children: <Widget>[
-                Container(key: keyOne, height: 50.0, width: 500.0),
-                Container(key: keyTwo, height: 50.0, width: 500.0),
+                SizedBox(key: keyOne, height: 50.0, width: 500.0),
+                SizedBox(key: keyTwo, height: 50.0, width: 500.0),
               ],
             ),
           ),
@@ -527,8 +527,8 @@ void main() {
               // Set padding to zero to align buttons with edge of button bar.
               buttonPadding: EdgeInsets.zero,
               children: <Widget>[
-                Container(key: keyOne, height: 50.0, width: 500.0),
-                Container(key: keyTwo, height: 50.0, width: 500.0),
+                SizedBox(key: keyOne, height: 50.0, width: 500.0),
+                SizedBox(key: keyTwo, height: 50.0, width: 500.0),
               ],
             ),
           ),
@@ -560,8 +560,8 @@ void main() {
               // out upwards.
               overflowDirection: VerticalDirection.up,
               children: <Widget>[
-                Container(key: keyOne, height: 50.0, width: 500.0),
-                Container(key: keyTwo, height: 50.0, width: 500.0),
+                SizedBox(key: keyOne, height: 50.0, width: 500.0),
+                SizedBox(key: keyTwo, height: 50.0, width: 500.0),
               ],
             ),
           ),
@@ -586,8 +586,8 @@ void main() {
               // Set padding to zero to align buttons with edge of button bar.
               buttonPadding: EdgeInsets.zero,
               children: <Widget>[
-                Container(key: keyOne, height: 50.0, width: 500.0),
-                Container(key: keyTwo, height: 50.0, width: 500.0),
+                SizedBox(key: keyOne, height: 50.0, width: 500.0),
+                SizedBox(key: keyTwo, height: 50.0, width: 500.0),
               ],
             ),
           ),
@@ -614,8 +614,8 @@ void main() {
               // buttons in an overflow case.
               overflowButtonSpacing: 10.0,
               children: <Widget>[
-                Container(key: keyOne, height: 50.0, width: 500.0),
-                Container(key: keyTwo, height: 50.0, width: 500.0),
+                SizedBox(key: keyOne, height: 50.0, width: 500.0),
+                SizedBox(key: keyTwo, height: 50.0, width: 500.0),
               ],
             ),
           ),

packages/flutter/test/material/button_theme_test.dart

@@ -242,7 +242,7 @@ void main() {
                 return Container(
                   alignment: Alignment.center,
                   child: DropdownButtonHideUnderline(
-                    child: Container(
+                    child: SizedBox(
                       width: 200.0,
                       child: DropdownButton<String>(
                         key: dropdownKey,

packages/flutter/test/material/chip_test.dart

@@ -105,12 +105,12 @@ Future<void> _testConstrainedLabel(
   await tester.pumpWidget(
     _wrapForChip(
       child: Center(
-        child: Container(
+        child: SizedBox(
           width: chipParentWidth,
           height: chipParentHeight,
           child: Chip(
             avatar: avatar,
-            label: Container(
+            label: SizedBox(
               key: labelKey,
               width: labelWidth,
               height: labelHeight,
@@ -321,13 +321,13 @@ void main() {
       await tester.pumpWidget(
         _wrapForChip(
           child: Center(
-            child: Container(
+            child: SizedBox(
               width: 500.0,
               height: 500.0,
               child: Column(
                 children: <Widget>[
                   Chip(
-                    label: Container(
+                    label: SizedBox(
                       key: labelKey,
                       width: labelWidth,
                       height: labelHeight,
@@ -396,7 +396,7 @@ void main() {
       Widget chipBuilder (String text, {Widget? avatar, VoidCallback? onDeleted}) {
         return MaterialApp(
           home: Scaffold(
-            body: Container(
+            body: SizedBox(
               width: 150,
               child: Column(
                 children: <Widget>[
@@ -634,7 +634,7 @@ void main() {
             ),
             Chip(
               avatar: const CircleAvatar(child: Text('B')),
-              label: Container(key: keyB, width: 10.0, height: 10.0),
+              label: SizedBox(key: keyB, width: 10.0, height: 10.0),
             ),
           ],
         ),
@@ -662,7 +662,7 @@ void main() {
         child: Column(
           children: <Widget>[
             Chip(
-              avatar: Container(key: keyA, width: 20.0, height: 20.0),
+              avatar: SizedBox(key: keyA, width: 20.0, height: 20.0),
               label: const Text('Chip A'),
             ),
           ],
@@ -680,7 +680,7 @@ void main() {
         child: Column(
           children: <Widget>[
             Chip(
-              deleteIcon: Container(key: keyA, width: 20.0, height: 20.0),
+              deleteIcon: SizedBox(key: keyA, width: 20.0, height: 20.0),
               label: const Text('Chip A'),
               onDeleted: () { },
             ),
@@ -706,7 +706,7 @@ void main() {
                   child: Center(
                     child: Chip(
                       avatar: Placeholder(key: keyA),
-                      label: Container(
+                      label: SizedBox(
                         key: keyB,
                         width: 40.0,
                         height: 40.0,
@@ -743,7 +743,7 @@ void main() {
                   child: Center(
                     child: Chip(
                       avatar: Placeholder(key: keyA),
-                      label: Container(
+                      label: SizedBox(
                         key: keyB,
                         width: 40.0,
                         height: 40.0,
@@ -1226,13 +1226,13 @@ void main() {
     // With avatar, but not selectable.
     final UniqueKey avatarKey = UniqueKey();
     await pushChip(
-      avatar: Container(width: 40.0, height: 40.0, key: avatarKey),
+      avatar: SizedBox(width: 40.0, height: 40.0, key: avatarKey),
     );
     expect(tester.getSize(find.byType(RawChip)), equals(const Size(104.0, 48.0)));
 
     // Turn on selection.
     await pushChip(
-      avatar: Container(width: 40.0, height: 40.0, key: avatarKey),
+      avatar: SizedBox(width: 40.0, height: 40.0, key: avatarKey),
       selectable: true,
     );
     await tester.pumpAndSettle();
@@ -1384,7 +1384,7 @@ void main() {
 
     final UniqueKey avatarKey = UniqueKey();
     await pushChip(
-      avatar: Container(width: 40.0, height: 40.0, key: avatarKey),
+      avatar: SizedBox(width: 40.0, height: 40.0, key: avatarKey),
       selectable: true,
     );
     await tester.pumpAndSettle();

packages/flutter/test/material/divider_test.dart

@@ -130,7 +130,7 @@ void main() {
     await tester.pumpWidget(
       MaterialApp(
         home: Material(
-          child: Container(
+          child: SizedBox(
             height: 24.0,
             child: Row(
               children: const <Widget>[

packages/flutter/test/material/dropdown_test.dart

@@ -1601,7 +1601,7 @@ void main() {
       itemHeight: null,
       selectedItemBuilder: (BuildContext context) {
         return items.map<Widget>((String item) {
-          return Container(
+          return SizedBox(
             height: double.parse(item),
             width: double.parse(item),
             child: Center(child: Text(item)),
@@ -1629,16 +1629,16 @@ void main() {
       await tester.pumpWidget(buildFrame(
         value: null,
         // [hint] widget is smaller than largest selected item widget
-        hint: Container(
+        hint: const SizedBox(
           height: 50,
           width: 50,
-          child: const Text('hint')
+          child: Text('hint')
         ),
         items: items,
         itemHeight: null,
         selectedItemBuilder: (BuildContext context) {
           return items.map<Widget>((String item) {
-            return Container(
+            return SizedBox(
               height: double.parse(item),
               width: double.parse(item),
               child: Center(child: Text(item)),
@@ -1671,16 +1671,16 @@ void main() {
         // to the largest item regardless of which one is selected.
         value: selectedItem,
         // [hint] widget is larger than largest selected item widget
-        hint: Container(
+        hint: const SizedBox(
           height: 125,
           width: 125,
-          child: const Text('hint')
+          child: Text('hint'),
         ),
         items: items,
         itemHeight: null,
         selectedItemBuilder: (BuildContext context) {
           return items.map<Widget>((String item) {
-            return Container(
+            return SizedBox(
               height: double.parse(item),
               width: double.parse(item),
               child: Center(child: Text(item)),
@@ -1709,16 +1709,16 @@ void main() {
       await tester.pumpWidget(buildFrame(
         value: null,
         // [hint] widget is smaller than largest selected item widget
-        hint: Container(
+        hint: const SizedBox(
           height: 50,
           width: 50,
-          child: const Text('hint')
+          child: Text('hint'),
         ),
         items: items,
         itemHeight: null,
         selectedItemBuilder: (BuildContext context) {
           return items.map<Widget>((String item) {
-            return Container(
+            return SizedBox(
               height: double.parse(item),
               width: double.parse(item),
               child: Center(child: Text(item)),
@@ -1747,16 +1747,16 @@ void main() {
       await tester.pumpWidget(buildFrame(
         value: null,
         // [hint] widget is larger than largest selected item widget
-        hint: Container(
+        hint: const SizedBox(
           height: 125,
           width: 125,
-          child: const Text('hint')
+          child: Text('hint')
         ),
         items: items,
         itemHeight: null,
         selectedItemBuilder: (BuildContext context) {
           return items.map<Widget>((String item) {
-            return Container(
+            return SizedBox(
               height: double.parse(item),
               width: double.parse(item),
               child: Center(child: Text(item)),
@@ -1785,16 +1785,16 @@ void main() {
       await tester.pumpWidget(buildFrame(
         value: null,
         // [hint] widget is smaller than largest selected item widget
-        disabledHint: Container(
+        disabledHint: const SizedBox(
           height: 50,
           width: 50,
-          child: const Text('hint')
+          child: Text('hint')
         ),
         items: items,
         itemHeight: null,
         selectedItemBuilder: (BuildContext context) {
           return items.map<Widget>((String item) {
-            return Container(
+            return SizedBox(
               height: double.parse(item),
               width: double.parse(item),
               child: Center(child: Text(item)),
@@ -1823,16 +1823,16 @@ void main() {
       await tester.pumpWidget(buildFrame(
         value: null,
         // [hint] widget is larger than largest selected item widget
-        disabledHint: Container(
+        disabledHint: const SizedBox(
           height: 125,
           width: 125,
-          child: const Text('hint')
+          child: Text('hint')
         ),
         items: items,
         itemHeight: null,
         selectedItemBuilder: (BuildContext context) {
           return items.map<Widget>((String item) {
-            return Container(
+            return SizedBox(
               height: double.parse(item),
               width: double.parse(item),
               child: Center(child: Text(item)),

packages/flutter/test/material/expansion_tile_test.dart

@@ -297,15 +297,15 @@ void main() {
   });
 
   testWidgets('ExpansionTile expandedAlignment test', (WidgetTester tester) async {
-    await tester.pumpWidget(MaterialApp(
+    await tester.pumpWidget(const MaterialApp(
       home: Material(
         child: Center(
           child: ExpansionTile(
-            title: const Text('title'),
+            title: Text('title'),
             expandedAlignment: Alignment.centerLeft,
             children: <Widget>[
-              Container(height: 100, width: 100),
-              Container(height: 100, width: 80),
+              SizedBox(height: 100, width: 100),
+              SizedBox(height: 100, width: 80),
             ],
           ),
         ),
@@ -339,9 +339,9 @@ void main() {
             // and expandedCrossAxisAlignment later in the test.
             expandedAlignment: Alignment.centerRight,
             expandedCrossAxisAlignment: CrossAxisAlignment.start,
-            children: <Widget>[
-              Container(height: 100, width: 100, key: child0Key),
-              Container(height: 100, width: 80, key: child1Key),
+            children: const <Widget>[
+              SizedBox(height: 100, width: 100, key: child0Key),
+              SizedBox(height: 100, width: 80, key: child1Key),
             ],
           ),
         ),
@@ -391,14 +391,14 @@ void main() {
   testWidgets('expandedCrossAxisAlignment and expandedAlignment default values', (WidgetTester tester) async {
     const Key child1Key = Key('child1');
 
-    await tester.pumpWidget(MaterialApp(
+    await tester.pumpWidget(const MaterialApp(
       home: Material(
         child: Center(
           child: ExpansionTile(
-            title: const Text('title'),
+            title: Text('title'),
             children: <Widget>[
-              Container(height: 100, width: 100),
-              Container(height: 100, width: 80, key: child1Key),
+              SizedBox(height: 100, width: 100),
+              SizedBox(height: 100, width: 80, key: child1Key),
             ],
           ),
         ),
@@ -424,18 +424,20 @@ void main() {
   });
 
   testWidgets('childrenPadding default value', (WidgetTester tester) async {
-    await tester.pumpWidget(MaterialApp(
-      home: Material(
-        child: Center(
-          child: ExpansionTile(
-            title: const Text('title'),
-            children: <Widget>[
-              Container(height: 100, width: 100),
-            ],
+    await tester.pumpWidget(
+      const MaterialApp(
+        home: Material(
+          child: Center(
+            child: ExpansionTile(
+              title: Text('title'),
+              children: <Widget>[
+                SizedBox(height: 100, width: 100),
+              ],
+            ),
           ),
         ),
       ),
-    ));
+    );
 
     await tester.tap(find.text('title'));
     await tester.pumpAndSettle();
@@ -452,19 +454,21 @@ void main() {
   });
 
   testWidgets('ExpansionTile childrenPadding test', (WidgetTester tester) async {
-    await tester.pumpWidget(MaterialApp(
-      home: Material(
-        child: Center(
-          child: ExpansionTile(
-            title: const Text('title'),
-            childrenPadding: const EdgeInsets.fromLTRB(10, 8, 12, 4),
-            children: <Widget>[
-              Container(height: 100, width: 100),
-            ],
+    await tester.pumpWidget(
+      const MaterialApp(
+        home: Material(
+          child: Center(
+            child: ExpansionTile(
+              title: Text('title'),
+              childrenPadding: EdgeInsets.fromLTRB(10, 8, 12, 4),
+              children: <Widget>[
+                SizedBox(height: 100, width: 100),
+              ],
+            ),
           ),
         ),
       ),
-    ));
+    );
 
     await tester.tap(find.text('title'));
     await tester.pumpAndSettle();

packages/flutter/test/material/flexible_space_bar_test.dart

@@ -141,7 +141,7 @@ void main() {
                 delegate: SliverChildListDelegate(
                   <Widget>[
                     for (int i = 0; i < 50; i++)
-                      Container(
+                      SizedBox(
                         height: 200,
                         child: Center(child: Text('Item $i')),
                       ),

packages/flutter/test/material/floating_action_button_location_test.dart

@@ -624,9 +624,9 @@ void main() {
           data: data,
           child: Scaffold(
             resizeToAvoidBottomInset: resizeToAvoidBottomInset,
-            bottomSheet: bottomSheet ? Container(
+            bottomSheet: bottomSheet ? const SizedBox(
               height: 100,
-              child: const Center(child: Text('BottomSheet')),
+              child: Center(child: Text('BottomSheet')),
             ) : null,
             appBar: appBar ? AppBar(title: const Text('Demo')) : null,
             bottomNavigationBar: bottomNavigationBar ? BottomNavigationBar(

packages/flutter/test/material/ink_paint_test.dart

@@ -45,7 +45,7 @@ void main() {
         textDirection: TextDirection.ltr,
         child: Material(
           child: Center(
-            child: Container(
+            child: SizedBox(
               width: 200.0,
               height: 60.0,
               child: InkWell(
@@ -94,7 +94,7 @@ void main() {
         textDirection: TextDirection.ltr,
         child: Material(
           child: Center(
-            child: Container(
+            child: SizedBox(
               width: 100.0,
               height: 100.0,
               child: InkWell(
@@ -267,7 +267,7 @@ void main() {
             textDirection: TextDirection.ltr,
             child: Material(
               child: Center(
-                child: Container(
+                child: SizedBox(
                   width: 100.0,
                   height: 100.0,
                   child: InkWell(
@@ -358,7 +358,7 @@ void main() {
         textDirection: TextDirection.ltr,
         child: Material(
           child: Center(
-            child: Container(
+            child: SizedBox(
               width: 100.0,
               height: 100.0,
               child: InkWell(
@@ -394,7 +394,7 @@ void main() {
         textDirection: TextDirection.ltr,
         child: Material(
           child: Center(
-            child: Container(
+            child: SizedBox(
               width: 100.0,
               height: 100.0,
               child: InkWell(

packages/flutter/test/material/ink_well_test.dart

@@ -128,7 +128,7 @@ void main() {
       child: Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             width: 100,
             height: 100,
             child: InkWell(
@@ -147,7 +147,7 @@ void main() {
     final TestGesture gesture = await tester.createGesture(kind: PointerDeviceKind.mouse);
     await gesture.addPointer();
     addTearDown(gesture.removePointer);
-    await gesture.moveTo(tester.getCenter(find.byType(Container)));
+    await gesture.moveTo(tester.getCenter(find.byType(SizedBox)));
     await tester.pumpAndSettle();
     final RenderObject inkFeatures = tester.allRenderObjects.firstWhere((RenderObject object) => object.runtimeType.toString() == '_RenderInkFeatures');
     expect(inkFeatures, paints..rect(rect: const Rect.fromLTRB(350.0, 250.0, 450.0, 350.0), color: const Color(0xff00ff00)));
@@ -160,7 +160,7 @@ void main() {
       child: Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             width: 100,
             height: 100,
             child: InkWell(
@@ -184,7 +184,7 @@ void main() {
     final TestGesture gesture = await tester.createGesture(kind: PointerDeviceKind.mouse);
     await gesture.addPointer();
     addTearDown(gesture.removePointer);
-    await gesture.moveTo(tester.getCenter(find.byType(Container)));
+    await gesture.moveTo(tester.getCenter(find.byType(SizedBox)));
     await tester.pumpAndSettle();
     final RenderObject inkFeatures = tester.allRenderObjects.firstWhere((RenderObject object) => object.runtimeType.toString() == '_RenderInkFeatures');
     expect(inkFeatures, paints..rect(rect: const Rect.fromLTRB(350.0, 250.0, 450.0, 350.0), color: const Color(0xff00ff00)));
@@ -198,7 +198,7 @@ void main() {
         child: Directionality(
           textDirection: TextDirection.ltr,
           child: Center(
-            child: Container(
+            child: SizedBox(
               width: 100,
               height: 100,
               child: InkWell(
@@ -235,7 +235,7 @@ void main() {
         child: Directionality(
           textDirection: TextDirection.ltr,
           child: Center(
-            child: Container(
+            child: SizedBox(
               width: 100,
               height: 100,
               child: InkWell(
@@ -278,7 +278,7 @@ void main() {
         child: Center(
           child: Focus(
             focusNode: focusNode,
-            child: Container(
+            child: SizedBox(
               width: 100,
               height: 100,
               child: InkWell(
@@ -316,7 +316,7 @@ void main() {
         child: Center(
           child: Focus(
             focusNode: focusNode,
-            child: Container(
+            child: SizedBox(
               width: 100,
               height: 100,
               child: InkWell(
@@ -354,7 +354,7 @@ void main() {
         child: Directionality(
           textDirection: TextDirection.ltr,
           child: Center(
-            child: Container(
+            child: SizedBox(
               width: 100,
               height: 100,
               child: InkResponse(
@@ -383,7 +383,7 @@ void main() {
       child: Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             width: 100,
             height: 100,
             child: InkWell(
@@ -573,9 +573,9 @@ void main() {
                 addAutomaticKeepAlives: keepAlive,
                 dragStartBehavior: DragStartBehavior.down,
                 children: <Widget>[
-                  Container(height: 500.0, child: InkWell(onTap: () {}, child: const Placeholder())),
-                  Container(height: 500.0),
-                  Container(height: 500.0),
+                  SizedBox(height: 500.0, child: InkWell(onTap: () {}, child: const Placeholder())),
+                  const SizedBox(height: 500.0),
+                  const SizedBox(height: 500.0),
                 ],
               ),
             ),
@@ -721,7 +721,7 @@ void main() {
       Material(
         child: Directionality(
           textDirection: TextDirection.ltr,
-          child: Container(
+          child: SizedBox(
             width: 100,
             height: 100,
             child: InkWell(
@@ -730,7 +730,7 @@ void main() {
               onLongPress: () {},
               onHover: (bool value) { hovering = value; },
               focusNode: focusNode,
-              child: Container(key: childKey),
+              child: SizedBox(key: childKey),
             ),
           ),
         ),
@@ -749,13 +749,13 @@ void main() {
       Material(
         child: Directionality(
           textDirection: TextDirection.ltr,
-          child: Container(
+          child: SizedBox(
             width: 100,
             height: 100,
             child: InkWell(
               focusNode: focusNode,
               onHover: (bool value) { hovering = value; },
-              child: Container(key: childKey),
+              child: SizedBox(key: childKey),
             ),
           ),
         ),
@@ -790,7 +790,7 @@ void main() {
                 key: middleKey,
                 child: paddedInkWell(
                   key: innerKey,
-                  child: Container(width: 50, height: 50),
+                  child: const SizedBox(width: 50, height: 50),
                 ),
               ),
             ),
@@ -852,7 +852,7 @@ void main() {
           textDirection: TextDirection.ltr,
           child: Align(
             alignment: Alignment.topLeft,
-            child: Container(
+            child: SizedBox(
               width: 200,
               height: 100,
               child: Row(
@@ -863,7 +863,7 @@ void main() {
                       key: innerKey,
                     ),
                   ),
-                  Container(),
+                  const SizedBox(),
                 ],
               ),
             ),
@@ -885,7 +885,7 @@ void main() {
           textDirection: TextDirection.ltr,
           child: Align(
             alignment: Alignment.topLeft,
-            child: Container(
+            child: SizedBox(
               width: 200,
               height: 100,
               child: Row(
@@ -944,7 +944,7 @@ void main() {
                 key: middleKey,
                 child: paddedInkWell(
                   key: innerKey,
-                  child: Container(width: 50, height: 50),
+                  child: const SizedBox(width: 50, height: 50),
                 ),
               ),
             ),
@@ -974,19 +974,19 @@ void main() {
         child: Directionality(
           textDirection: TextDirection.ltr,
           child: Center(
-            child: Container(
+            child: SizedBox(
               width: 100,
               height: 100,
               child: InkWell(
                 key: parentKey,
                 onTap: () {},
                 child: Center(
-                  child: Container(
+                  child: SizedBox(
                     width: 100,
                     height: 50,
                     child: Row(
                       children: <Widget>[
-                        Container(
+                        SizedBox(
                           width: 50,
                           height: 50,
                           child: InkWell(
@@ -994,7 +994,7 @@ void main() {
                             onTap: () {},
                           ),
                         ),
-                        Container(
+                        SizedBox(
                           width: 50,
                           height: 50,
                           child: InkWell(
@@ -1071,19 +1071,19 @@ void main() {
           textDirection: TextDirection.ltr,
           child: Align(
             alignment: Alignment.topLeft,
-            child: Container(
+            child: SizedBox(
               width: leftWidth+rightWidth,
               height: 100,
               child: Row(
                 children: <Widget>[
-                  Container(
+                  SizedBox(
                     width: leftWidth,
                     height: 100,
                     child: InkWell(
                       key: leftKey,
                       onTap: () {},
                       child: Center(
-                        child: Container(
+                        child: SizedBox(
                           width: leftWidth,
                           height: 50,
                           child: leftChild,
@@ -1091,14 +1091,14 @@ void main() {
                       ),
                     ),
                   ),
-                  Container(
+                  SizedBox(
                     width: rightWidth,
                     height: 100,
                     child: InkWell(
                       key: rightKey,
                       onTap: () {},
                       child: Center(
-                        child: Container(
+                        child: SizedBox(
                           width: leftWidth,
                           height: 50,
                           child: rightChild,
@@ -1176,13 +1176,13 @@ void main() {
           child: GestureDetector(
             onHorizontalDragStart: (_) {},
             child: Center(
-              child: Container(
+              child: SizedBox(
                 width: 100,
                 height: 100,
                 child: InkWell(
                   onTap: () {},
                   child: Center(
-                    child: Container(
+                    child: SizedBox(
                       width: 50,
                       height: 50,
                       child: InkWell(

packages/flutter/test/material/input_decorator_test.dart

@@ -1330,8 +1330,8 @@ void main() {
       buildInputDecorator(
         // isEmpty: false (default)
         // isFocused: false (default)
-        decoration: InputDecoration(
-          prefix: Container(
+        decoration: const InputDecoration(
+          prefix: SizedBox(
             key: pKey,
             height: 100,
             width: 10,
@@ -1374,9 +1374,9 @@ void main() {
       buildInputDecorator(
         // isEmpty: false (default)
         // isFocused: false (default)
-        decoration: InputDecoration(
-          border: const OutlineInputBorder(),
-          prefix: Container(
+        decoration: const InputDecoration(
+          border: OutlineInputBorder(),
+          prefix: SizedBox(
             key: pKey,
             height: 100,
             width: 10,
@@ -1905,8 +1905,8 @@ void main() {
           buildInputDecorator(
             // isEmpty: false (default)
             // isFocused: false (default)
-            decoration: InputDecoration(
-              prefix: Container(
+            decoration: const InputDecoration(
+              prefix: SizedBox(
                 key: pKey,
                 height: 100,
                 width: 10,
@@ -1934,8 +1934,8 @@ void main() {
           buildInputDecorator(
             // isEmpty: false (default)
             // isFocused: false (default)
-            decoration: InputDecoration(
-              prefix: Container(
+            decoration: const InputDecoration(
+              prefix: SizedBox(
                 key: pKey,
                 height: 100,
                 width: 10,
@@ -1963,8 +1963,8 @@ void main() {
           buildInputDecorator(
             // isEmpty: false (default)
             // isFocused: false (default)
-            decoration: InputDecoration(
-              prefix: Container(
+            decoration: const InputDecoration(
+              prefix: SizedBox(
                 key: pKey,
                 height: 100,
                 width: 10,
@@ -1995,9 +1995,9 @@ void main() {
             // isEmpty: false (default)
             // isFocused: false (default)
             expands: true,
-            decoration: InputDecoration(
-              border: const OutlineInputBorder(),
-              prefix: Container(
+            decoration: const InputDecoration(
+              border: OutlineInputBorder(),
+              prefix: SizedBox(
                 key: pKey,
                 height: 100,
                 width: 10,
@@ -2026,9 +2026,9 @@ void main() {
             // isEmpty: false (default)
             // isFocused: false (default)
             expands: true,
-            decoration: InputDecoration(
-              border: const OutlineInputBorder(),
-              prefix: Container(
+            decoration: const InputDecoration(
+              border: OutlineInputBorder(),
+              prefix: SizedBox(
                 key: pKey,
                 height: 100,
                 width: 10,
@@ -2059,9 +2059,9 @@ void main() {
             // isEmpty: false (default)
             // isFocused: false (default)
             expands: true,
-            decoration: InputDecoration(
-              border: const OutlineInputBorder(),
-              prefix: Container(
+            decoration: const InputDecoration(
+              border: OutlineInputBorder(),
+              prefix: SizedBox(
                 key: pKey,
                 height: 100,
                 width: 10,
@@ -2090,9 +2090,9 @@ void main() {
             // isEmpty: false (default)
             // isFocused: false (default)
             expands: true,
-            decoration: InputDecoration(
-              border: const OutlineInputBorder(),
-              prefix: Container(
+            decoration: const InputDecoration(
+              border: OutlineInputBorder(),
+              prefix: SizedBox(
                 key: pKey,
                 height: 100,
                 width: 10,
@@ -4109,7 +4109,7 @@ void main() {
 
     await tester.pumpWidget(
       Center(
-        child: Container(
+        child: SizedBox(
           width: 100,
           height: 100,
           child: buildInputDecorator(
@@ -4132,7 +4132,7 @@ void main() {
 
     await tester.pumpWidget(
       Center(
-        child: Container(
+        child: SizedBox(
           width: 100,
           height: 100,
           child: buildInputDecorator(
@@ -4260,7 +4260,7 @@ void main() {
 
     Widget getLabeledInputDecorator(FloatingLabelBehavior floatingLabelBehavior) => MaterialApp(
         home: Material(
-          child: Container(
+          child: SizedBox(
             width: 300,
             child: TextField(
               decoration: InputDecoration(
@@ -4361,7 +4361,7 @@ void main() {
     await tester.pumpWidget(MaterialApp(
       home: Material(
         child: Center(
-          child: Container(
+          child: SizedBox(
             width: 200,
             height: 28,
             child: TextField(

packages/flutter/test/material/list_tile_test.dart

@@ -72,10 +72,10 @@ void main() {
           child: Material(
             child: Center(
               child: ListTile(
-                leading: Container(key: leadingKey, width: 24.0, height: 24.0),
+                leading: SizedBox(key: leadingKey, width: 24.0, height: 24.0),
                 title: const Text('title'),
                 subtitle: hasSubtitle ? Text('subtitle', textScaleFactor: subtitleScaleFactor) : null,
-                trailing: Container(key: trailingKey, width: 24.0, height: 24.0),
+                trailing: SizedBox(key: trailingKey, width: 24.0, height: 24.0),
                 dense: dense,
                 isThreeLine: isThreeLine,
               ),

packages/flutter/test/material/material_test.dart

@@ -232,9 +232,9 @@ void main() {
                 },
                 child: null,
               ),
-              Material(
+              const Material(
                 type: MaterialType.transparency,
-                child: Container(
+                child: SizedBox(
                   width: 400.0,
                   height: 500.0,
                 ),

packages/flutter/test/material/persistent_bottom_sheet_test.dart

@@ -59,10 +59,10 @@ void main() {
             return ListView(
               controller: controller,
               shrinkWrap: true,
-              children: <Widget>[
-                Container(height: 100.0, child: const Text('One')),
-                Container(height: 100.0, child: const Text('Two')),
-                Container(height: 100.0, child: const Text('Three')),
+              children: const <Widget>[
+                SizedBox(height: 100.0, child: Text('One')),
+                SizedBox(height: 100.0, child: Text('Two')),
+                SizedBox(height: 100.0, child: Text('Three')),
               ],
             );
           },
@@ -94,10 +94,10 @@ void main() {
       return ListView(
         shrinkWrap: true,
         primary: false,
-        children: <Widget>[
-          Container(height: 100.0, child: const Text('One')),
-          Container(height: 100.0, child: const Text('Two')),
-          Container(height: 100.0, child: const Text('Three')),
+        children: const <Widget>[
+          SizedBox(height: 100.0, child: Text('One')),
+          SizedBox(height: 100.0, child: Text('Two')),
+          SizedBox(height: 100.0, child: Text('Three')),
         ],
       );
     });
@@ -126,10 +126,10 @@ void main() {
       return ListView(
         shrinkWrap: true,
         primary: false,
-        children: <Widget>[
-          Container(height: 100.0, child: const Text('One')),
-          Container(height: 100.0, child: const Text('Two')),
-          Container(height: 100.0, child: const Text('Three')),
+        children: const <Widget>[
+          SizedBox(height: 100.0, child: Text('One')),
+          SizedBox(height: 100.0, child: Text('Two')),
+          SizedBox(height: 100.0, child: Text('Three')),
         ],
       );
     });
@@ -165,10 +165,10 @@ void main() {
             return ListView(
               shrinkWrap: true,
               controller: controller,
-              children: <Widget>[
-                Container(height: 100.0, child: const Text('One')),
-                Container(height: 100.0, child: const Text('Two')),
-                Container(height: 100.0, child: const Text('Three')),
+              children: const <Widget>[
+                SizedBox(height: 100.0, child: Text('One')),
+                SizedBox(height: 100.0, child: Text('Two')),
+                SizedBox(height: 100.0, child: Text('Three')),
               ],
             );
           },
@@ -319,18 +319,18 @@ void main() {
             return ListView(
               controller: controller,
               shrinkWrap: true,
-              children: <Widget>[
-                Container(height: 100.0, child: const Text('One')),
-                Container(height: 100.0, child: const Text('Two')),
-                Container(height: 100.0, child: const Text('Three')),
-                Container(height: 100.0, child: const Text('Three')),
-                Container(height: 100.0, child: const Text('Three')),
-                Container(height: 100.0, child: const Text('Three')),
-                Container(height: 100.0, child: const Text('Three')),
-                Container(height: 100.0, child: const Text('Three')),
-                Container(height: 100.0, child: const Text('Three')),
-                Container(height: 100.0, child: const Text('Three')),
-                Container(height: 100.0, child: const Text('Three')),
+              children: const <Widget>[
+                SizedBox(height: 100.0, child: Text('One')),
+                SizedBox(height: 100.0, child: Text('Two')),
+                SizedBox(height: 100.0, child: Text('Three')),
+                SizedBox(height: 100.0, child: Text('Three')),
+                SizedBox(height: 100.0, child: Text('Three')),
+                SizedBox(height: 100.0, child: Text('Three')),
+                SizedBox(height: 100.0, child: Text('Three')),
+                SizedBox(height: 100.0, child: Text('Three')),
+                SizedBox(height: 100.0, child: Text('Three')),
+                SizedBox(height: 100.0, child: Text('Three')),
+                SizedBox(height: 100.0, child: Text('Three')),
               ],
             );
           },
@@ -516,10 +516,10 @@ void main() {
       return ListView(
         shrinkWrap: true,
         primary: false,
-        children: <Widget>[
-          Container(height: 100.0, child: const Text('One')),
-          Container(height: 100.0, child: const Text('Two')),
-          Container(height: 100.0, child: const Text('Three')),
+        children: const <Widget>[
+          SizedBox(height: 100.0, child: Text('One')),
+          SizedBox(height: 100.0, child: Text('Two')),
+          SizedBox(height: 100.0, child: Text('Three')),
         ],
       );
     }, backgroundColor: color, elevation: elevation, shape: shape, clipBehavior: clipBehavior);

packages/flutter/test/material/raw_material_button_test.dart

@@ -241,7 +241,7 @@ void main() {
             RawMaterialButton(
             materialTapTargetSize: MaterialTapTargetSize.padded,
             onPressed: () { },
-            child: Container(
+            child: SizedBox(
               width: 400.0,
               height: 400.0,
               child: Column(

packages/flutter/test/material/refresh_indicator_test.dart

@@ -63,7 +63,7 @@ void main() {
           onRefresh: refresh,
           child: SingleChildScrollView(
             scrollDirection: Axis.horizontal,
-            child: Container(
+            child: SizedBox(
               width: 600.0,
               child: ListView(
                 physics: const AlwaysScrollableScrollPhysics(),

packages/flutter/test/material/reorderable_list_test.dart

@@ -1276,7 +1276,7 @@ void main() {
     await tester.pumpWidget(MaterialApp(
       home: ReorderableListView.builder(
         itemBuilder: (BuildContext context, int index) {
-          return Container(
+          return SizedBox(
             key: ValueKey<int>(items[index]),
             height: 100,
             child: ReorderableDragStartListener(
@@ -1350,7 +1350,7 @@ class _StatefulState extends State<_Stateful> {
 
   @override
   Widget build(BuildContext context) {
-    return Container(
+    return SizedBox(
       width: 48.0,
       height: 48.0,
       child: Material(

packages/flutter/test/material/scaffold_test.dart

@@ -949,7 +949,7 @@ void main() {
                   ),
                 ),
               ],
-              drawer: Container(
+              drawer: SizedBox(
                 key: drawer,
                 width: 204.0,
                 child: SafeArea(
@@ -1051,7 +1051,7 @@ void main() {
                   ),
                 ),
               ],
-              drawer: Container(
+              drawer: SizedBox(
                 key: drawer,
                 width: 204.0,
                 child: SafeArea(
@@ -2108,7 +2108,7 @@ void main() {
                   scaffoldMessenger = ScaffoldMessenger.maybeOf(context);
                 },
                 behavior: HitTestBehavior.opaque,
-                child: Container(
+                child: const SizedBox(
                   height: 100.0,
                   width: 100.0,
                 ),
@@ -2145,7 +2145,7 @@ void main() {
                   ScaffoldMessenger.of(context);
                 },
                 behavior: HitTestBehavior.opaque,
-                child: Container(
+                child: const SizedBox(
                   height: 100.0,
                   width: 100.0,
                 ),

packages/flutter/test/material/scrollbar_test.dart

@@ -67,15 +67,15 @@ void main() {
             width: 300.0,
             child: Scrollbar(
               child: ListView(
-                children: <Widget>[
-                  Container(height: 40.0, child: const Text('0')),
-                  Container(height: 40.0, child: const Text('1')),
-                  Container(height: 40.0, child: const Text('2')),
-                  Container(height: 40.0, child: const Text('3')),
-                  Container(height: 40.0, child: const Text('4')),
-                  Container(height: 40.0, child: const Text('5')),
-                  Container(height: 40.0, child: const Text('6')),
-                  Container(height: 40.0, child: const Text('7')),
+                children: const <Widget>[
+                  SizedBox(height: 40.0, child: Text('0')),
+                  SizedBox(height: 40.0, child: Text('1')),
+                  SizedBox(height: 40.0, child: Text('2')),
+                  SizedBox(height: 40.0, child: Text('3')),
+                  SizedBox(height: 40.0, child: Text('4')),
+                  SizedBox(height: 40.0, child: Text('5')),
+                  SizedBox(height: 40.0, child: Text('6')),
+                  SizedBox(height: 40.0, child: Text('7')),
                 ],
               ),
             ),
@@ -101,13 +101,13 @@ void main() {
 
   testWidgets('ScrollbarPainter does not divide by zero', (WidgetTester tester) async {
     await tester.pumpWidget(
-      _buildBoilerplate(child: Container(
+      _buildBoilerplate(child: SizedBox(
         height: 200.0,
         width: 300.0,
         child: Scrollbar(
           child: ListView(
-            children: <Widget>[
-              Container(height: 40.0, child: const Text('0')),
+            children: const <Widget>[
+              SizedBox(height: 40.0, child: Text('0')),
             ],
           ),
         ),

packages/flutter/test/material/snack_bar_test.dart

@@ -24,7 +24,7 @@ void main() {
                 ));
               },
               behavior: HitTestBehavior.opaque,
-              child: Container(
+              child: const SizedBox(
                 height: 100.0,
                 width: 100.0,
               ),
@@ -69,7 +69,7 @@ void main() {
                 ));
               },
               behavior: HitTestBehavior.opaque,
-              child: Container(
+              child: const SizedBox(
                 height: 100.0,
                 width: 100.0,
               ),
@@ -115,7 +115,7 @@ void main() {
                 ));
               },
               behavior: HitTestBehavior.opaque,
-              child: Container(
+              child: const SizedBox(
                 height: 100.0,
                 width: 100.0,
               ),
@@ -190,7 +190,7 @@ void main() {
                 ));
               },
               behavior: HitTestBehavior.opaque,
-              child: Container(
+              child: const SizedBox(
                 height: 100.0,
                 width: 100.0,
               ),
@@ -267,7 +267,7 @@ void main() {
                 ));
               },
               behavior: HitTestBehavior.opaque,
-              child: Container(
+              child: const SizedBox(
                 height: 100.0,
                 width: 100.0,
               ),
@@ -353,7 +353,7 @@ void main() {
                 ));
               },
               behavior: HitTestBehavior.opaque,
-              child: Container(
+              child: const SizedBox(
                 height: 100.0,
                 width: 100.0,
               ),
@@ -437,7 +437,7 @@ void main() {
                 ));
               },
               behavior: HitTestBehavior.opaque,
-              child: Container(
+              child: const SizedBox(
                 height: 100.0,
                 width: 100.0,
               ),
@@ -482,7 +482,7 @@ void main() {
                 ));
               },
               behavior: HitTestBehavior.opaque,
-              child: Container(
+              child: const SizedBox(
                 height: 100.0,
                 width: 100.0,
               ),
@@ -1603,7 +1603,7 @@ void main() {
                 ));
               },
               behavior: HitTestBehavior.opaque,
-              child: Container(
+              child: const SizedBox(
                 height: 100.0,
                 width: 100.0,
               ),
@@ -1751,7 +1751,7 @@ void main() {
                 ));
               },
               behavior: HitTestBehavior.opaque,
-              child: Container(
+              child: const SizedBox(
                 height: 100.0,
                 width: 100.0,
               ),
@@ -1795,7 +1795,7 @@ void main() {
                 ));
               },
               behavior: HitTestBehavior.opaque,
-              child: Container(
+              child: const SizedBox(
                 height: 100.0,
                 width: 100.0,
               ),
@@ -2344,7 +2344,7 @@ void main() {
                   ));
                 },
                 behavior: HitTestBehavior.opaque,
-                child: Container(
+                child: const SizedBox(
                   height: 100.0,
                   width: 100.0,
                 ),

packages/flutter/test/material/text_field_test.dart

@@ -529,13 +529,13 @@ void main() {
 
   testWidgets('text field selection toolbar renders correctly inside opacity', (WidgetTester tester) async {
     await tester.pumpWidget(
-      MaterialApp(
+      const MaterialApp(
         home: Scaffold(
           body: Center(
-            child: Container(
+            child: SizedBox(
               width: 100,
               height: 100,
-              child: const Opacity(
+              child: Opacity(
                 opacity: 0.5,
                 child: TextField(
                   decoration: InputDecoration(hintText: 'Placeholder'),
@@ -2406,7 +2406,7 @@ void main() {
       Widget? prefix,
     }) {
       return boilerplate(
-        child: Container(
+        child: SizedBox(
           height: height,
           child: TextField(
             key: textFieldKey,
@@ -3173,9 +3173,9 @@ void main() {
   testWidgets('Can align to center', (WidgetTester tester) async {
     await tester.pumpWidget(
       overlay(
-        child: Container(
+        child: const SizedBox(
           width: 300.0,
-          child: const TextField(
+          child: TextField(
             textAlign: TextAlign.center,
             decoration: null,
           ),
@@ -3207,9 +3207,9 @@ void main() {
   testWidgets('Can align to center within center', (WidgetTester tester) async {
     await tester.pumpWidget(
       overlay(
-        child: Container(
+        child: const SizedBox(
           width: 300.0,
-          child: const Center(
+          child: Center(
             child: TextField(
               textAlign: TextAlign.center,
               decoration: null,
@@ -3528,7 +3528,7 @@ void main() {
 
     await tester.pumpWidget(
       overlay(
-        child: Container(
+        child: SizedBox(
           width: 100.0,
           child: TextField(
             controller: controller,
@@ -3609,7 +3609,7 @@ void main() {
 
     await tester.pumpWidget(
       overlay(
-        child: Container(
+        child: SizedBox(
           width: 100.0,
           child: TextField(
             controller: controller,
@@ -8177,9 +8177,9 @@ void main() {
   testWidgets('Caret center position', (WidgetTester tester) async {
     await tester.pumpWidget(
       overlay(
-        child: Container(
+        child: const SizedBox(
           width: 300.0,
-          child: const TextField(
+          child: TextField(
             textAlign: TextAlign.center,
             decoration: null,
           ),
@@ -8217,9 +8217,9 @@ void main() {
   testWidgets('Caret indexes into trailing whitespace center align', (WidgetTester tester) async {
     await tester.pumpWidget(
       overlay(
-        child: Container(
+        child: const SizedBox(
           width: 300.0,
-          child: const TextField(
+          child: TextField(
             textAlign: TextAlign.center,
             decoration: null,
           ),
@@ -8836,7 +8836,7 @@ void main() {
             mainAxisAlignment: MainAxisAlignment.center,
             mainAxisSize: MainAxisSize.min,
             children: <Widget>[
-              Container(
+              SizedBox(
                 width: 100.0,
                 child: TextField(
                   controller: controller1,
@@ -8847,21 +8847,21 @@ void main() {
                   mainAxisAlignment: MainAxisAlignment.center,
                   mainAxisSize: MainAxisSize.min,
                   children: <Widget>[
-                    Container(
+                    SizedBox(
                       width: 100.0,
                       child: TextField(
                         controller: controller2,
                         focusNode: focusNode2,
                       ),
                     ),
-                    Container(
+                    SizedBox(
                       width: 100.0,
                       child: TextField(
                         controller: controller3,
                         focusNode: focusNode3,
                       ),
                     ),
-                    Container(
+                    SizedBox(
                       width: 100.0,
                       child: TextField(
                         controller: controller4,
@@ -8870,7 +8870,7 @@ void main() {
                     ),
                   ],
                 ),
-              Container(
+              SizedBox(
                 width: 100.0,
                 child: TextField(
                   controller: controller5,
@@ -9140,7 +9140,7 @@ void main() {
         child: StatefulBuilder(
           builder: (BuildContext context, StateSetter setter) {
             setState = setter;
-            return Container(
+            return SizedBox(
               width: isWide ? wideWidth : narrowWidth,
               child: TextField(
                 key: textFieldKey,

packages/flutter/test/material/text_selection_toolbar_test.dart

@@ -52,6 +52,13 @@ class _CustomMaterialTextSelectionControls extends MaterialTextSelectionControls
   }
 }
 
+class TestBox extends SizedBox {
+  const TestBox({Key? key}) : super(key: key, width: itemWidth, height: itemHeight);
+
+  static const double itemHeight = 44.0;
+  static const double itemWidth = 100.0;
+}
+
 void main() {
   TestWidgetsFlutterBinding.ensureInitialized();
 
@@ -72,17 +79,7 @@ void main() {
 
   testWidgets('puts children in an overflow menu if they overflow', (WidgetTester tester) async {
     late StateSetter setState;
-    const double height = 44.0;
-    const double itemWidth = 100.0;
-    final List<Widget> children = <Widget>[
-      Container(width: itemWidth, height: height),
-      Container(width: itemWidth, height: height),
-      Container(width: itemWidth, height: height),
-      Container(width: itemWidth, height: height),
-      Container(width: itemWidth, height: height),
-      Container(width: itemWidth, height: height),
-      Container(width: itemWidth, height: height),
-    ];
+    final List<Widget> children = List<Widget>.generate(7, (int i) => const TestBox());
 
     await tester.pumpWidget(
       MaterialApp(
@@ -102,29 +99,29 @@ void main() {
     );
 
     // All children fit on the screen, so they are all rendered.
-    expect(find.byType(Container), findsNWidgets(children.length));
+    expect(find.byType(TestBox), findsNWidgets(children.length));
     expect(_findOverflowButton(), findsNothing);
 
     // Adding one more child makes the children overflow.
     setState(() {
       children.add(
-        Container(width: itemWidth, height: height),
+        const TestBox(),
       );
     });
     await tester.pumpAndSettle();
-    expect(find.byType(Container), findsNWidgets(children.length - 1));
+    expect(find.byType(TestBox), findsNWidgets(children.length - 1));
     expect(_findOverflowButton(), findsOneWidget);
 
     // Tap the overflow button to show the overflow menu.
     await tester.tap(_findOverflowButton());
     await tester.pumpAndSettle();
-    expect(find.byType(Container), findsNWidgets(1));
+    expect(find.byType(TestBox), findsNWidgets(1));
     expect(_findOverflowButton(), findsOneWidget);
 
     // Tap the overflow button again to hide the overflow menu.
     await tester.tap(_findOverflowButton());
     await tester.pumpAndSettle();
-    expect(find.byType(Container), findsNWidgets(children.length - 1));
+    expect(find.byType(TestBox), findsNWidgets(children.length - 1));
     expect(_findOverflowButton(), findsOneWidget);
   });
 

packages/flutter/test/material/time_picker_theme_test.dart

@@ -460,7 +460,7 @@ Material _dayPeriodMaterial(WidgetTester tester) {
 }
 
 Container _dayPeriodDivider(WidgetTester tester) {
-  return tester.widget<Container>(find.descendant(of: find.byWidgetPredicate((Widget w) => '${w.runtimeType}' == '_DayPeriodControl'), matching: find.byType(Container)).at(1));
+  return tester.widget<Container>(find.descendant(of: find.byWidgetPredicate((Widget w) => '${w.runtimeType}' == '_DayPeriodControl'), matching: find.byType(Container)).at(0));
 }
 
 IconButton _entryModeIconButton(WidgetTester tester) {

packages/flutter/test/rendering/viewport_test.dart

@@ -51,13 +51,13 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 200.0,
             width: 300.0,
             child: ListView(
               controller: ScrollController(initialScrollOffset: 300.0),
               children: children = List<Widget>.generate(20, (int i) {
-                return Container(
+                return SizedBox(
                   height: 100.0,
                   width: 300.0,
                   child: Text('Tile $i'),
@@ -96,14 +96,14 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 300.0,
             width: 200.0,
             child: ListView(
               scrollDirection: Axis.horizontal,
               controller: ScrollController(initialScrollOffset: 300.0),
               children: children = List<Widget>.generate(20, (int i) {
-                return Container(
+                return SizedBox(
                   height: 300.0,
                   width: 100.0,
                   child: Text('Tile $i'),
@@ -142,14 +142,14 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 200.0,
             width: 300.0,
             child: ListView(
               controller: ScrollController(initialScrollOffset: 300.0),
               reverse: true,
               children: children = List<Widget>.generate(20, (int i) {
-                return Container(
+                return SizedBox(
                   height: 100.0,
                   width: 300.0,
                   child: Text('Tile $i'),
@@ -188,7 +188,7 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 300.0,
             width: 200.0,
             child: ListView(
@@ -196,7 +196,7 @@ void main() {
               reverse: true,
               controller: ScrollController(initialScrollOffset: 300.0),
               children: children = List<Widget>.generate(20, (int i) {
-                return Container(
+                return SizedBox(
                   height: 300.0,
                   width: 100.0,
                   child: Text('Tile $i'),
@@ -234,14 +234,14 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 200.0,
             width: 300.0,
             child: CustomScrollView(
               controller: ScrollController(initialScrollOffset: 300.0),
               slivers: List<Widget>.generate(20, (int i) {
                 final Widget sliver = SliverToBoxAdapter(
-                  child: Container(
+                  child: SizedBox(
                     height: 100.0,
                     child: Text('Tile $i'),
                   ),
@@ -280,7 +280,7 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 300.0,
             width: 200.0,
             child: CustomScrollView(
@@ -288,7 +288,7 @@ void main() {
               controller: ScrollController(initialScrollOffset: 300.0),
               slivers: List<Widget>.generate(20, (int i) {
                 final Widget sliver = SliverToBoxAdapter(
-                    child: Container(
+                    child: SizedBox(
                       width: 100.0,
                       child: Text('Tile $i'),
                     ),
@@ -327,7 +327,7 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 200.0,
             width: 300.0,
             child: CustomScrollView(
@@ -335,7 +335,7 @@ void main() {
               reverse: true,
               slivers: List<Widget>.generate(20, (int i) {
                 final Widget sliver = SliverToBoxAdapter(
-                    child: Container(
+                    child: SizedBox(
                       height: 100.0,
                       child: Text('Tile $i'),
                     ),
@@ -372,21 +372,21 @@ void main() {
   testWidgets('Viewport getOffsetToReveal Sliver - up - reverse growth', (WidgetTester tester) async {
     const Key centerKey = ValueKey<String>('center');
     const EdgeInsets padding = EdgeInsets.only(top: 22.0, bottom: 23.0);
-    final Widget centerSliver = SliverPadding(
+    const Widget centerSliver = SliverPadding(
       key: centerKey,
       padding: padding,
       sliver: SliverToBoxAdapter(
-        child: Container(
+        child: SizedBox(
           height: 100.0,
-          child: const Text('Tile center'),
+          child: Text('Tile center'),
         ),
       ),
     );
-    final Widget lowerItem = Container(
+    const Widget lowerItem = SizedBox(
       height: 100.0,
-      child: const Text('Tile lower'),
+      child: Text('Tile lower'),
     );
-    final Widget lowerSliver = SliverPadding(
+    const Widget lowerSliver = SliverPadding(
       padding: padding,
       sliver: SliverToBoxAdapter(
         child: lowerItem,
@@ -394,10 +394,10 @@ void main() {
     );
 
     await tester.pumpWidget(
-      Directionality(
+      const Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 200.0,
             width: 300.0,
             child: CustomScrollView(
@@ -429,21 +429,21 @@ void main() {
   testWidgets('Viewport getOffsetToReveal Sliver - left - reverse growth', (WidgetTester tester) async {
     const Key centerKey = ValueKey<String>('center');
     const EdgeInsets padding = EdgeInsets.only(left: 22.0, right: 23.0);
-    final Widget centerSliver = SliverPadding(
+    const Widget centerSliver = SliverPadding(
       key: centerKey,
       padding: padding,
       sliver: SliverToBoxAdapter(
-        child: Container(
+        child: SizedBox(
           width: 100.0,
-          child: const Text('Tile center'),
+          child: Text('Tile center'),
         ),
       ),
     );
-    final Widget lowerItem = Container(
+    const Widget lowerItem = SizedBox(
       width: 100.0,
-      child: const Text('Tile lower'),
+      child: Text('Tile lower'),
     );
-    final Widget lowerSliver = SliverPadding(
+    const Widget lowerSliver = SliverPadding(
       padding: padding,
       sliver: SliverToBoxAdapter(
         child: lowerItem,
@@ -451,10 +451,10 @@ void main() {
     );
 
     await tester.pumpWidget(
-      Directionality(
+      const Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 200.0,
             width: 300.0,
             child: CustomScrollView(
@@ -490,7 +490,7 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 300.0,
             width: 200.0,
             child: CustomScrollView(
@@ -499,7 +499,7 @@ void main() {
               controller: ScrollController(initialScrollOffset: 300.0),
               slivers: List<Widget>.generate(20, (int i) {
                 final Widget sliver = SliverToBoxAdapter(
-                    child: Container(
+                    child: SizedBox(
                       width: 100.0,
                       child: Text('Tile $i'),
                     ),
@@ -537,7 +537,7 @@ void main() {
     final ScrollController controllerY  = ScrollController(initialScrollOffset: 400.0);
     final List<List<Widget>> children = List<List<Widget>>.generate(10, (int y) {
       return List<Widget>.generate(10, (int x) {
-        return Container(
+        return SizedBox(
           height: 100.0,
           width: 100.0,
           child: Text('$x,$y'),
@@ -567,13 +567,13 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 200.0,
             width: 200.0,
             child: ListView(
               controller: controllerY,
               children: List<Widget>.generate(10, (int y) {
-                return Container(
+                return SizedBox(
                   height: 100.0,
                   child: ListView(
                     scrollDirection: Axis.horizontal,
@@ -694,7 +694,7 @@ void main() {
 
   group('Nested viewports (same orientation) showOnScreen', () {
     final List<Widget> children = List<Widget>.generate(10, (int i) {
-      return Container(
+      return SizedBox(
         height: 100.0,
         width: 300.0,
         child: Text('$i'),
@@ -706,16 +706,16 @@ void main() {
         Directionality(
           textDirection: TextDirection.ltr,
           child: Center(
-            child: Container(
+            child: SizedBox(
               height: 200.0,
               width: 300.0,
               child: ListView(
                 controller: outer,
                 children: <Widget>[
-                  Container(
+                  const SizedBox(
                     height: 200.0,
                   ),
-                  Container(
+                  SizedBox(
                     height: 200.0,
                     width: 300.0,
                     child: ListView(
@@ -723,7 +723,7 @@ void main() {
                       children: children,
                     ),
                   ),
-                  Container(
+                  const SizedBox(
                     height: 200.0,
                   ),
                 ],
@@ -896,16 +896,16 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 200.0,
             width: 200.0,
             child: ListView(
               controller: controllerY,
               children: <Widget>[
-                Container(
+                const SizedBox(
                   height: 150.0,
                 ),
-                Container(
+                SizedBox(
                   height: 100.0,
                   child: ListView(
                     physics: const PageScrollPhysics(), // Turns off `allowImplicitScrolling`
@@ -921,7 +921,7 @@ void main() {
                     ],
                   ),
                 ),
-                Container(
+                const SizedBox(
                   height: 150.0,
                 ),
               ],
@@ -946,16 +946,16 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 200.0,
             width: 200.0,
             child: ListView(
               controller: controllerY,
               children: <Widget>[
-                Container(
+                const SizedBox(
                   height: 150.0,
                 ),
-                Container(
+                SizedBox(
                   height: 100.0,
                   child: CustomScrollView(
                     physics: const PageScrollPhysics(), // Turns off `allowImplicitScrolling`
@@ -981,7 +981,7 @@ void main() {
                     ],
                   ),
                 ),
-                Container(
+                const SizedBox(
                   height: 150.0,
                 ),
               ],
@@ -1005,12 +1005,12 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 200.0,
             child: ListView(
               controller: controller = ScrollController(initialScrollOffset: 300.0),
               children: children = List<Widget>.generate(20, (int i) {
-                return Container(
+                return SizedBox(
                   height: 300.0,
                   child: Text('Tile $i'),
                 );
@@ -1068,7 +1068,7 @@ void main() {
         Directionality(
           textDirection: TextDirection.ltr,
           child: Center(
-            child: Container(
+            child: SizedBox(
               height: 600.0,
               child: CustomScrollView(
                 controller: controller = ScrollController(initialScrollOffset: 300.0),
@@ -1084,7 +1084,7 @@ void main() {
                     ),
                   )
                   : SliverToBoxAdapter(
-                    child: Container(
+                    child: SizedBox(
                       height: 300.0,
                       child: Text('Tile $i'),
                     ),
@@ -1134,7 +1134,7 @@ void main() {
       return Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 400.0,
             width: 400.0,
             child: CustomScrollView(
@@ -1146,7 +1146,7 @@ void main() {
                   ? floatingHeader
                   : SliverToBoxAdapter(
                     key: (i == 19) ? const Key('19') : null,
-                    child: Container(
+                    child: SizedBox(
                       height: 300.0,
                       width: 300,
                       child: Text('Tile $i'),
@@ -1437,7 +1437,7 @@ void main() {
       return Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 400.0,
             width: 400.0,
             child: CustomScrollView(
@@ -1545,14 +1545,14 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 300.0,
             child: CustomScrollView(
               cacheExtent: 0,
               controller: outerController,
               slivers: <Widget>[
                 SliverToBoxAdapter(
-                  child: Container(
+                  child: SizedBox(
                     height: 300,
                     child: CustomScrollView(
                       controller: innerController,
@@ -1580,7 +1580,7 @@ void main() {
       ),
     );
 
-    tester.renderObject(find.widgetWithText(SizedBox, 'Tile 1', skipOffstage: false)).showOnScreen();
+    tester.renderObject(find.widgetWithText(SizedBox, 'Tile 1', skipOffstage: false).first).showOnScreen();
     await tester.pumpAndSettle();
     // The inner viewport scrolls to reveal the 2nd tile.
     expect(innerController.offset, 300.0);

packages/flutter/test/widgets/actions_test.dart

@@ -425,7 +425,7 @@ void main() {
                 },
                 onShowHoverHighlight: (bool value) => hovering = value,
                 onShowFocusHighlight: (bool value) => focusing = value,
-                child: Container(width: 100, height: 100, key: containerKey),
+                child: SizedBox(width: 100, height: 100, key: containerKey),
               ),
             ),
           ),
@@ -800,7 +800,7 @@ void main() {
                 },
                 onShowHoverHighlight: supplyCallbacks ? (bool value) => hovering = value : null,
                 onShowFocusHighlight: supplyCallbacks ? (bool value) => focusing = value : null,
-                child: Container(width: 100, height: 100, key: key),
+                child: SizedBox(width: 100, height: 100, key: key),
               ),
             ),
           ),

packages/flutter/test/widgets/align_test.dart

@@ -114,10 +114,10 @@ void main() {
         child: Row(
           crossAxisAlignment: CrossAxisAlignment.start,
           mainAxisAlignment: MainAxisAlignment.center,
-          children: <Widget>[
+          children: const <Widget>[
             Align(
               widthFactor: 0.5,
-              child: Container(
+              child: SizedBox(
                 height: 100.0,
                 width: 100.0,
               ),
@@ -137,11 +137,11 @@ void main() {
         child: Column(
           mainAxisAlignment: MainAxisAlignment.center,
           crossAxisAlignment: CrossAxisAlignment.start,
-          children: <Widget>[
+          children: const <Widget>[
             Align(
               alignment: Alignment.center,
               heightFactor: 0.5,
-              child: Container(
+              child: SizedBox(
                 height: 100.0,
                 width: 100.0,
               ),

packages/flutter/test/widgets/animated_align_test.dart

@@ -63,13 +63,13 @@ void main() {
         textDirection: TextDirection.ltr,
         child: Row(
           mainAxisSize: MainAxisSize.min,
-          children: <Widget>[
+          children: const <Widget>[
             AnimatedAlign(
               alignment: Alignment.center,
               curve: Curves.ease,
               widthFactor: 0.5,
-              duration: const Duration(milliseconds: 200),
-              child: Container(
+              duration: Duration(milliseconds: 200),
+              child: SizedBox(
                 height: 100.0,
                 width: 100.0,
               ),
@@ -87,13 +87,13 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Column(
-          children: <Widget>[
+          children: const <Widget>[
             AnimatedAlign(
               alignment: Alignment.center,
               curve: Curves.ease,
               heightFactor: 0.5,
-              duration: const Duration(milliseconds: 200),
-              child: Container(
+              duration: Duration(milliseconds: 200),
+              child: SizedBox(
                 height: 100.0,
                 width: 100.0,
               ),
@@ -112,12 +112,12 @@ void main() {
         textDirection: TextDirection.ltr,
         child: Column(
           mainAxisAlignment: MainAxisAlignment.center,
-          children: <Widget>[
+          children: const <Widget>[
             AnimatedAlign(
               alignment: Alignment.center,
               curve: Curves.ease,
-              duration: const Duration(milliseconds: 200),
-              child: Container(
+              duration: Duration(milliseconds: 200),
+              child: SizedBox(
                 height: 100.0,
                 width: 100.0,
               ),
@@ -126,7 +126,7 @@ void main() {
         ),
       ),
     );
-    final RenderBox box = tester.renderObject<RenderBox>(find.byType(Container));
+    final RenderBox box = tester.renderObject<RenderBox>(find.byType(SizedBox));
     expect(box.size, equals(const Size(100.0, 100)));
   });
 
@@ -138,12 +138,12 @@ void main() {
           child: Row(
             mainAxisSize: MainAxisSize.min,
             mainAxisAlignment: MainAxisAlignment.center,
-            children: <Widget>[
+            children: const <Widget>[
                AnimatedAlign(
                 alignment: Alignment.center,
                 curve: Curves.ease,
-                duration: const Duration(milliseconds: 200),
-                child: Container(
+                duration: Duration(milliseconds: 200),
+                child: SizedBox(
                   height: 100.0,
                   width: 100.0,
                 ),
@@ -153,7 +153,7 @@ void main() {
         ),
       ),
     );
-    final RenderBox box = tester.renderObject<RenderBox>(find.byType(Container));
+    final RenderBox box = tester.renderObject<RenderBox>(find.byType(SizedBox).last);
     expect(box.size, equals(const Size(100.0, 100)));
   });
 }

packages/flutter/test/widgets/automatic_keep_alive_test.dart

@@ -123,7 +123,7 @@ void tests({ required bool impliedMode }) {
           addSemanticIndexes: false,
           cacheExtent: 0.0,
           children: generateList(
-            Container(height: 12.3, child: const Placeholder()), // about 50 widgets visible
+            const SizedBox(height: 12.3, child: Placeholder()), // about 50 widgets visible
             impliedMode: impliedMode,
           ),
         ),
@@ -231,7 +231,7 @@ void main() {
           cacheExtent: 0.0,
           children: <Widget>[
             AutomaticKeepAlive(
-              child: Container(
+              child: SizedBox(
                 height: 400.0,
                 child: Stack(children: const <Widget>[
                   Leaf(key: GlobalObjectKey<_LeafState>(0), child: Placeholder()),
@@ -239,15 +239,15 @@ void main() {
                 ]),
               ),
             ),
-            AutomaticKeepAlive(
-              child: Container(
-                key: const GlobalObjectKey<_LeafState>(2),
+            const AutomaticKeepAlive(
+              child: SizedBox(
+                key: GlobalObjectKey<_LeafState>(2),
                 height: 400.0,
               ),
             ),
-            AutomaticKeepAlive(
-              child: Container(
-                key: const GlobalObjectKey<_LeafState>(3),
+            const AutomaticKeepAlive(
+              child: SizedBox(
+                key: GlobalObjectKey<_LeafState>(3),
                 height: 400.0,
               ),
             ),
@@ -315,7 +315,7 @@ void main() {
           cacheExtent: 0.0,
           children: <Widget>[
             AutomaticKeepAlive(
-              child: Container(
+              child: SizedBox(
                 height: 400.0,
                 child: Stack(children: const <Widget>[
                   Leaf(key: GlobalObjectKey<_LeafState>(0), child: Placeholder()),
@@ -324,7 +324,7 @@ void main() {
               ),
             ),
             AutomaticKeepAlive(
-              child: Container(
+              child: SizedBox(
                 height: 400.0,
                 child: Stack(children: const <Widget>[
                   Leaf(key: GlobalObjectKey<_LeafState>(2), child: Placeholder()),
@@ -333,7 +333,7 @@ void main() {
               ),
             ),
             AutomaticKeepAlive(
-              child: Container(
+              child: SizedBox(
                 height: 400.0,
                 child: Stack(children: const <Widget>[
                   Leaf(key: GlobalObjectKey<_LeafState>(4), child: Placeholder()),
@@ -371,7 +371,7 @@ void main() {
         cacheExtent: 0.0,
         children: <Widget>[
           AutomaticKeepAlive(
-            child: Container(
+            child: SizedBox(
               height: 400.0,
               child: Stack(children: const <Widget>[
                 Leaf(key: GlobalObjectKey<_LeafState>(1), child: Placeholder()),
@@ -379,7 +379,7 @@ void main() {
             ),
           ),
           AutomaticKeepAlive(
-            child: Container(
+            child: SizedBox(
               height: 400.0,
               child: Stack(children: const <Widget>[
                 Leaf(key: GlobalObjectKey<_LeafState>(2), child: Placeholder()),
@@ -388,7 +388,7 @@ void main() {
             ),
           ),
           AutomaticKeepAlive(
-            child: Container(
+            child: SizedBox(
               height: 400.0,
               child: Stack(children: const <Widget>[
                 Leaf(key: GlobalObjectKey<_LeafState>(4), child: Placeholder()),
@@ -435,7 +435,7 @@ void main() {
         cacheExtent: 0.0,
         children: <Widget>[
           AutomaticKeepAlive(
-            child: Container(
+            child: SizedBox(
               height: 400.0,
               child: Stack(children: const <Widget>[
                 Leaf(key: GlobalObjectKey<_LeafState>(1), child: Placeholder()),
@@ -444,14 +444,14 @@ void main() {
             ),
           ),
           AutomaticKeepAlive(
-            child: Container(
+            child: SizedBox(
               height: 400.0,
               child: Stack(children: const <Widget>[
               ]),
             ),
           ),
           AutomaticKeepAlive(
-            child: Container(
+            child: SizedBox(
               height: 400.0,
               child: Stack(children: const <Widget>[
                 Leaf(key: GlobalObjectKey<_LeafState>(3), child: Placeholder()),
@@ -486,7 +486,7 @@ void main() {
               key: GlobalObjectKey<_AlwaysKeepAliveState>(0),
             );
           }
-          return Container(
+          return SizedBox(
             height: 44.0,
             child: Text('FooBar $index'),
           );
@@ -520,7 +520,7 @@ void main() {
               key: GlobalObjectKey<_AlwaysKeepAliveState>(index),
             );
           }
-          return Container(
+          return SizedBox(
             height: 44.0,
             child: Text('FooBar $index'),
           );
@@ -573,9 +573,9 @@ class _AlwaysKeepAliveState extends State<_AlwaysKeepAlive> with AutomaticKeepAl
   @override
   Widget build(BuildContext context) {
     super.build(context);
-    return Container(
+    return const SizedBox(
       height: 48.0,
-      child: const Text('keep me alive'),
+      child: Text('keep me alive'),
     );
   }
 }
@@ -591,9 +591,9 @@ class AlwaysKeepAliveRenderBoxState extends State<_AlwaysKeepAlive> with Automat
   @override
   Widget build(BuildContext context) {
     super.build(context);
-    return Container(
+    return const SizedBox(
       height: 48.0,
-      child: const Text('keep me alive'),
+      child: Text('keep me alive'),
     );
   }
 }

packages/flutter/test/widgets/column_test.dart

@@ -21,10 +21,10 @@ void main() {
     await tester.pumpWidget(Center(
       child: Column(
         key: columnKey,
-        children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0),
-          Expanded(child: Container(key: child1Key, width: 100.0, height: 100.0)),
-          Container(key: child2Key, width: 100.0, height: 100.0),
+        children: const <Widget>[
+          SizedBox(key: child0Key, width: 100.0, height: 100.0),
+          Expanded(child: SizedBox(key: child1Key, width: 100.0, height: 100.0)),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0),
         ],
       ),
     ));
@@ -67,10 +67,10 @@ void main() {
     await tester.pumpWidget(Center(
       child: Column(
         key: columnKey,
-        children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0),
-          Container(key: child1Key, width: 100.0, height: 100.0),
-          Container(key: child2Key, width: 100.0, height: 100.0),
+        children: const <Widget>[
+          SizedBox(key: child0Key, width: 100.0, height: 100.0),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0),
         ],
       ),
     ));
@@ -112,9 +112,9 @@ void main() {
       child: Column(
         key: columnKey,
         mainAxisAlignment: MainAxisAlignment.center,
-        children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0),
-          Container(key: child1Key, width: 100.0, height: 100.0),
+        children: const <Widget>[
+          SizedBox(key: child0Key, width: 100.0, height: 100.0),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0),
         ],
       ),
     ));
@@ -151,10 +151,10 @@ void main() {
       child: Column(
         key: columnKey,
         mainAxisAlignment: MainAxisAlignment.end,
-        children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0),
-          Container(key: child1Key, width: 100.0, height: 100.0),
-          Container(key: child2Key, width: 100.0, height: 100.0),
+        children: const <Widget>[
+          SizedBox(key: child0Key, width: 100.0, height: 100.0),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0),
         ],
       ),
     ));
@@ -197,10 +197,10 @@ void main() {
       child: Column(
         key: columnKey,
         mainAxisAlignment: MainAxisAlignment.spaceBetween,
-        children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0),
-          Container(key: child1Key, width: 100.0, height: 100.0),
-          Container(key: child2Key, width: 100.0, height: 100.0),
+        children: const <Widget>[
+          SizedBox(key: child0Key, width: 100.0, height: 100.0),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0),
         ],
       ),
     ));
@@ -244,11 +244,11 @@ void main() {
       child: Column(
         key: columnKey,
         mainAxisAlignment: MainAxisAlignment.spaceAround,
-        children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0),
-          Container(key: child1Key, width: 100.0, height: 100.0),
-          Container(key: child2Key, width: 100.0, height: 100.0),
-          Container(key: child3Key, width: 100.0, height: 100.0),
+        children: const <Widget>[
+          SizedBox(key: child0Key, width: 100.0, height: 100.0),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0),
+          SizedBox(key: child3Key, width: 100.0, height: 100.0),
         ],
       ),
     ));
@@ -297,10 +297,10 @@ void main() {
       child: Column(
         key: columnKey,
         mainAxisAlignment: MainAxisAlignment.spaceEvenly,
-        children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 20.0),
-          Container(key: child1Key, width: 100.0, height: 20.0),
-          Container(key: child2Key, width: 100.0, height: 20.0),
+        children: const <Widget>[
+          SizedBox(key: child0Key, width: 100.0, height: 20.0),
+          SizedBox(key: child1Key, width: 100.0, height: 20.0),
+          SizedBox(key: child2Key, width: 100.0, height: 20.0),
         ],
       ),
     ));
@@ -368,13 +368,13 @@ void main() {
     const Key childKey = Key('childKey');
 
     await tester.pumpWidget(Center(
-      child: Container(
+      child: SizedBox(
         width: 0.0,
         height: 0.0,
         child: Column(
           mainAxisSize: MainAxisSize.min,
-          children: <Widget>[
-            Container(
+          children: const <Widget>[
+            SizedBox(
               key: childKey,
               width: 100.0,
               height: 100.0,
@@ -405,10 +405,10 @@ void main() {
       child: Column(
         key: columnKey,
         verticalDirection: VerticalDirection.up,
-        children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0),
-          Expanded(child: Container(key: child1Key, width: 100.0, height: 100.0)),
-          Container(key: child2Key, width: 100.0, height: 100.0),
+        children: const <Widget>[
+          SizedBox(key: child0Key, width: 100.0, height: 100.0),
+          Expanded(child: SizedBox(key: child1Key, width: 100.0, height: 100.0)),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0),
         ],
       ),
     ));
@@ -452,10 +452,10 @@ void main() {
       child: Column(
         key: columnKey,
         verticalDirection: VerticalDirection.up,
-        children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0),
-          Container(key: child1Key, width: 100.0, height: 100.0),
-          Container(key: child2Key, width: 100.0, height: 100.0),
+        children: const <Widget>[
+          SizedBox(key: child0Key, width: 100.0, height: 100.0),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0),
         ],
       ),
     ));
@@ -498,9 +498,9 @@ void main() {
         key: columnKey,
         mainAxisAlignment: MainAxisAlignment.center,
         verticalDirection: VerticalDirection.up,
-        children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0),
-          Container(key: child1Key, width: 100.0, height: 100.0),
+        children: const <Widget>[
+          SizedBox(key: child0Key, width: 100.0, height: 100.0),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0),
         ],
       ),
     ));
@@ -538,10 +538,10 @@ void main() {
         key: columnKey,
         mainAxisAlignment: MainAxisAlignment.end,
         verticalDirection: VerticalDirection.up,
-        children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0),
-          Container(key: child1Key, width: 100.0, height: 100.0),
-          Container(key: child2Key, width: 100.0, height: 100.0),
+        children: const <Widget>[
+          SizedBox(key: child0Key, width: 100.0, height: 100.0),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0),
         ],
       ),
     ));
@@ -585,10 +585,10 @@ void main() {
         key: columnKey,
         mainAxisAlignment: MainAxisAlignment.spaceBetween,
         verticalDirection: VerticalDirection.up,
-        children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0),
-          Container(key: child1Key, width: 100.0, height: 100.0),
-          Container(key: child2Key, width: 100.0, height: 100.0),
+        children: const <Widget>[
+          SizedBox(key: child0Key, width: 100.0, height: 100.0),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0),
         ],
       ),
     ));
@@ -633,11 +633,11 @@ void main() {
         key: columnKey,
         mainAxisAlignment: MainAxisAlignment.spaceAround,
         verticalDirection: VerticalDirection.up,
-        children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0),
-          Container(key: child1Key, width: 100.0, height: 100.0),
-          Container(key: child2Key, width: 100.0, height: 100.0),
-          Container(key: child3Key, width: 100.0, height: 100.0),
+        children: const <Widget>[
+          SizedBox(key: child0Key, width: 100.0, height: 100.0),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0),
+          SizedBox(key: child3Key, width: 100.0, height: 100.0),
         ],
       ),
     ));
@@ -687,10 +687,10 @@ void main() {
         key: columnKey,
         mainAxisAlignment: MainAxisAlignment.spaceEvenly,
         verticalDirection: VerticalDirection.up,
-        children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 20.0),
-          Container(key: child1Key, width: 100.0, height: 20.0),
-          Container(key: child2Key, width: 100.0, height: 20.0),
+        children: const <Widget>[
+          SizedBox(key: child0Key, width: 100.0, height: 20.0),
+          SizedBox(key: child1Key, width: 100.0, height: 20.0),
+          SizedBox(key: child2Key, width: 100.0, height: 20.0),
         ],
       ),
     ));
@@ -760,14 +760,14 @@ void main() {
     const Key childKey = Key('childKey');
 
     await tester.pumpWidget(Center(
-      child: Container(
+      child: SizedBox(
         width: 0.0,
         height: 0.0,
         child: Column(
           mainAxisSize: MainAxisSize.min,
           verticalDirection: VerticalDirection.up,
-          children: <Widget>[
-            Container(
+          children: const <Widget>[
+            SizedBox(
               key: childKey,
               width: 100.0,
               height: 100.0,

packages/flutter/test/widgets/composited_transform_test.dart

@@ -35,7 +35,7 @@ void main() {
                   link: linkToUse ?? link,
                   targetAnchor: Alignment.center,
                   followerAnchor: Alignment.center,
-                  child: Container(key: key, height: 20.0, width: 20.0),
+                  child: SizedBox(key: key, height: 20.0, width: 20.0),
                 ),
               ),
             ],
@@ -76,7 +76,7 @@ void main() {
                 link: link,
                 targetAnchor: targetAlignment,
                 followerAnchor: followerAlignment,
-                child: Container(key: key, height: 20.0, width: 20.0),
+                child: SizedBox(key: key, height: 20.0, width: 20.0),
               ),
             ),
           ],
@@ -119,7 +119,7 @@ void main() {
                 angle: 1.0, // radians
                 child: CompositedTransformTarget(
                   link: link,
-                  child: Container(key: key1, width: 80.0, height: 10.0),
+                  child: SizedBox(key: key1, width: 80.0, height: 10.0),
                 ),
               ),
             ),
@@ -132,7 +132,7 @@ void main() {
                   link: link,
                   targetAnchor: targetAlignment,
                   followerAnchor: followerAlignment,
-                  child: Container(key: key2, width: 40.0, height: 20.0),
+                  child: SizedBox(key: key2, width: 40.0, height: 20.0),
                 ),
               ),
             ),
@@ -184,7 +184,7 @@ void main() {
                 angle: 1.0, // radians
                 child: CompositedTransformTarget(
                   link: link,
-                  child: Container(key: key1, width: 80.0, height: 10.0),
+                  child: SizedBox(key: key1, width: 80.0, height: 10.0),
                 ),
               ),
             ),
@@ -205,7 +205,7 @@ void main() {
                           link: link,
                           targetAnchor: targetAlignment,
                           followerAnchor: followerAlignment,
-                          child: Container(key: key2, width: 40.0, height: 20.0),
+                          child: SizedBox(key: key2, width: 40.0, height: 20.0),
                         ),
                       ),
                     ),
@@ -262,7 +262,7 @@ void main() {
               top: 456.0,
               child: CompositedTransformTarget(
                 link: link,
-                child: Container(key: key1, height: 10.0, width: 10.0),
+                child: SizedBox(key: key1, height: 10.0, width: 10.0),
               ),
             ),
             CompositedTransformFollower(
@@ -271,7 +271,7 @@ void main() {
                 key: key2,
                 behavior: HitTestBehavior.opaque,
                 onTap: () { tapped = true; },
-                child: Container(key: key3, height: 2.0, width: 2.0),
+                child: SizedBox(key: key3, height: 2.0, width: 2.0),
               ),
             ),
           ],

packages/flutter/test/widgets/dismissible_test.dart

@@ -46,7 +46,7 @@ Widget buildTest({
                 ? <DismissDirection, double>{}
                 : <DismissDirection, double>{DismissDirection.startToEnd: startToEndThreshold},
             crossAxisEndOffset: crossAxisEndOffset,
-            child: Container(
+            child: SizedBox(
               width: itemExtent,
               height: itemExtent,
               child: Text(item.toString()),
@@ -574,7 +574,7 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             width: 100.0,
             height: 1000.0,
             child: Column(
@@ -755,7 +755,7 @@ void main() {
                 background: background,
                 dismissThresholds: const <DismissDirection, double>{},
                 crossAxisEndOffset: crossAxisEndOffset,
-                child: Container(
+                child: SizedBox(
                   width: itemExtent,
                   height: itemExtent,
                   child: Text(1.toString()),

packages/flutter/test/widgets/draggable_test.dart

@@ -30,7 +30,7 @@ void main() {
           ),
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(height: 100.0, child: const Text('Target'));
+              return const SizedBox(height: 100.0, child: Text('Target'));
             },
             onMove: (_) => moveCount++,
             onAccept: accepted.add,
@@ -103,7 +103,7 @@ void main() {
           ),
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(height: 100.0, child: const Text('Target 1'));
+              return const SizedBox(height: 100.0, child: Text('Target 1'));
             },
             onLeave: (int? data) {
               if (data != null) {
@@ -113,7 +113,7 @@ void main() {
           ),
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(height: 100.0, child: const Text('Target 2'));
+              return const SizedBox(height: 100.0, child: Text('Target 2'));
             },
             onLeave: (int? data) {
               if (data != null) {
@@ -178,7 +178,7 @@ void main() {
           ),
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(height: 100.0, child: const Text('Target 1'));
+              return const SizedBox(height: 100.0, child: Text('Target 1'));
             },
             onLeave: (Object? data) {
               if (data is int) {
@@ -188,7 +188,7 @@ void main() {
           ),
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(height: 100.0, child: const Text('Target 2'));
+              return const SizedBox(height: 100.0, child: Text('Target 2'));
             },
             onLeave: (Object? data) {
               if (data is int) {
@@ -255,7 +255,7 @@ void main() {
           ),
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(height: 100.0, child: const Text('Target 1'));
+              return const SizedBox(height: 100.0, child: Text('Target 1'));
             },
             onMove: (DragTargetDetails<int> details) {
               targetMoveCount['Target 1'] =
@@ -264,7 +264,7 @@ void main() {
           ),
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(height: 100.0, child: const Text('Target 2'));
+              return const SizedBox(height: 100.0, child: Text('Target 2'));
             },
             onMove: (DragTargetDetails<int> details) {
               targetMoveCount['Target 2'] =
@@ -328,7 +328,7 @@ void main() {
           ),
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(height: 100.0, child: const Text('Target 1'));
+              return const SizedBox(height: 100.0, child: Text('Target 1'));
             },
             onMove: (DragTargetDetails<dynamic> details) {
               if (details.data is int) {
@@ -339,7 +339,7 @@ void main() {
           ),
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(height: 100.0, child: const Text('Target 2'));
+              return const SizedBox(height: 100.0, child: Text('Target 2'));
             },
             onMove: (DragTargetDetails<dynamic> details) {
               if (details.data is int) {
@@ -1163,7 +1163,7 @@ void main() {
           ),
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(height: 100.0, child: const Text('Target'));
+              return const SizedBox(height: 100.0, child: Text('Target'));
             },
             onAccept: accepted.add,
             onAcceptWithDetails: acceptedDetails.add,
@@ -1235,9 +1235,9 @@ void main() {
           ),
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(
+              return const SizedBox(
                 height: 100.0,
-                child: const Text('Target'),
+                child: Text('Target'),
               );
             },
             onWillAccept: (int? data) => false,
@@ -1311,10 +1311,7 @@ void main() {
         ),
         DragTarget<int>(
           builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-            return Container(
-              height: 100.0,
-              child: const Text('Target'),
-            );
+            return const SizedBox(height: 100.0, child: Text('Target'));
           },
           onWillAccept: (int? data) => false,
           onAccept: accepted.add,
@@ -1364,10 +1361,7 @@ void main() {
           ),
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(
-                height: 100.0,
-                child: const Text('Target'),
-              );
+              return const SizedBox(height: 100.0, child: Text('Target'));
             },
             onWillAccept: (int? data) => false,
             onAccept: accepted.add,
@@ -1434,7 +1428,7 @@ void main() {
           ),
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(
+              return SizedBox(
                 height: 100.0,
                 child: rejects.isNotEmpty
                     ? const Text('Rejected')
@@ -1492,7 +1486,7 @@ void main() {
           ),
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(
+              return SizedBox(
                 height: 100.0,
                 child: rejects.isNotEmpty
                     ? const Text('Rejected')
@@ -1577,9 +1571,9 @@ void main() {
           ),
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(
+              return const SizedBox(
                 height: 100.0,
-                child: const Text('Target'),
+                child: Text('Target'),
               );
             },
             onWillAccept: (int? data) => false,
@@ -1649,7 +1643,7 @@ void main() {
           ),
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(height: 100.0, child: const Text('Target'));
+              return const SizedBox(height: 100.0, child: Text('Target'));
             },
             onAccept: accepted.add,
             onAcceptWithDetails: acceptedDetails.add,
@@ -1790,7 +1784,7 @@ void main() {
           ),
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(height: 100.0, child: const Text('Target'));
+              return const SizedBox(height: 100.0, child: Text('Target'));
             },
             onAccept: accepted.add,
             onAcceptWithDetails: acceptedDetails.add,
@@ -1863,10 +1857,10 @@ void main() {
             children: <Widget>[
               DragTarget<int>(
                 builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-                  return IgnorePointer(
-                    child: Container(
+                  return const IgnorePointer(
+                    child: SizedBox(
                       height: 100.0,
-                      child: const Text('Target1'),
+                      child: Text('Target1'),
                     ),
                   );
                 },
@@ -1875,10 +1869,10 @@ void main() {
               ),
               DragTarget<double>(
                 builder: (BuildContext context, List<double?> data, List<dynamic> rejects) {
-                  return IgnorePointer(
-                    child: Container(
+                  return const IgnorePointer(
+                    child: SizedBox(
                       height: 100.0,
-                      child: const Text('Target2'),
+                      child: Text('Target2'),
                     ),
                   );
                 },
@@ -1992,10 +1986,10 @@ void main() {
             children: <Widget>[
               DragTarget<DragTargetData>(
                 builder: (BuildContext context, List<DragTargetData?> data, List<dynamic> rejects) {
-                  return IgnorePointer(
-                    child: Container(
+                  return const IgnorePointer(
+                    child: SizedBox(
                       height: 100.0,
-                      child: const Text('Target1'),
+                      child: Text('Target1'),
                     ),
                   );
                 }, onAccept: acceptedDragTargetDatas.add,
@@ -2003,10 +1997,10 @@ void main() {
               ),
               DragTarget<ExtendedDragTargetData>(
                 builder: (BuildContext context, List<ExtendedDragTargetData?> data, List<dynamic> rejects) {
-                  return IgnorePointer(
-                    child: Container(
+                  return const IgnorePointer(
+                    child: SizedBox(
                       height: 100.0,
-                      child: const Text('Target2'),
+                      child: Text('Target2'),
                     ),
                   );
                 },
@@ -2058,7 +2052,7 @@ void main() {
             ),
             DragTarget<int>(
               builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-                return Container(height: 100.0, child: const Text('Target'));
+                return const SizedBox(height: 100.0, child: Text('Target'));
               },
               onAccept: accepted.add,
               onAcceptWithDetails: acceptedDetails.add,
@@ -2317,7 +2311,7 @@ void main() {
           ),
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(height: 100.0, child: const Text('Target'));
+              return const SizedBox(height: 100.0, child: Text('Target'));
             },
             onAccept: accepted.add,
             onAcceptWithDetails: acceptedDetails.add,
@@ -2347,7 +2341,7 @@ void main() {
         children: <Widget>[
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(height: 100.0, child: const Text('Target'));
+              return const SizedBox(height: 100.0, child: Text('Target'));
             },
             onAccept: accepted.add,
             onAcceptWithDetails: acceptedDetails.add,
@@ -2427,7 +2421,7 @@ void main() {
           ),
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(height: 100.0, child: const Text('Target'));
+              return const SizedBox(height: 100.0, child: Text('Target'));
             },
             onAccept: accepted.add,
             onAcceptWithDetails: acceptedDetails.add,
@@ -2512,7 +2506,7 @@ void main() {
           ),
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(height: 100.0, child: const Text('Target'));
+              return const SizedBox(height: 100.0, child: Text('Target'));
             },
             onAccept: accepted.add,
             onAcceptWithDetails: acceptedDetails.add,
@@ -2696,7 +2690,7 @@ void main() {
         navigatorKey: rootNavigatorKey,
         home: Column(
           children: <Widget>[
-            Container(
+            SizedBox(
               height: 200.0,
               child: Navigator(
                 key: childNavigatorKey,
@@ -2718,8 +2712,8 @@ void main() {
             ),
             DragTarget<int>(
               builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-                return Container(
-                    height: 300.0, child: const Center(child: Text('Target 1')),
+                return const SizedBox(
+                    height: 300.0, child: Center(child: Text('Target 1')),
                 );
               },
             ),
@@ -2765,7 +2759,7 @@ void main() {
           ),
           DragTarget<Object>(
             builder: (BuildContext context, List<Object?> data, List<dynamic> rejects) {
-              return Container(height: 100.0, child: const Text('Target'));
+              return const SizedBox(height: 100.0, child: Text('Target'));
             },
             onAccept: accepted.add,
           ),
@@ -2801,7 +2795,7 @@ void main() {
           ),
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(height: 100.0, child: const Text('Target'));
+              return const SizedBox(height: 100.0, child: Text('Target'));
             },
             onAccept: accepted.add,
           ),
@@ -2837,7 +2831,7 @@ void main() {
           ),
           DragTarget<int>(
             builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-              return Container(height: 100.0, child: const Text('Target'));
+              return const SizedBox(height: 100.0, child: Text('Target'));
             },
             onAccept: accepted.add,
             onWillAccept: (int? data) {
@@ -3033,11 +3027,11 @@ void main() {
     await tester.pumpWidget(
       MaterialApp(
         home: Column(
-          children: <Widget>[
+          children: const <Widget>[
             Draggable<int>(
               hitTestBehavior: hitTestBehavior,
-              feedback: Container(height: 50.0, child: const Text('Draggable')),
-              child: Container(height: 50.0, child: const Text('Target')),
+              feedback: SizedBox(height: 50.0, child: Text('Draggable')),
+              child: SizedBox(height: 50.0, child: Text('Target')),
             ),
           ],
         ),
@@ -3058,7 +3052,7 @@ void main() {
               hitTestBehavior: hitTestBehavior,
               builder: (BuildContext context, List<int?> data,
                   List<dynamic> rejects) {
-                return Container(height: 100.0, child: const Text('Target'));
+                return const SizedBox(height: 100.0, child: Text('Target'));
               },
             ),
           ],
@@ -3139,7 +3133,7 @@ Future<void> _testChildAnchorFeedbackPosition({ required WidgetTester tester, do
                 ),
                 DragTarget<int>(
                   builder: (BuildContext context, List<int?> data, List<dynamic> rejects) {
-                    return Container(height: 100.0, child: const Text('Target'));
+                    return const SizedBox(height: 100.0, child: Text('Target'));
                   },
                   onAccept: accepted.add,
                   onAcceptWithDetails: acceptedDetails.add,

packages/flutter/test/widgets/editable_text_show_on_screen_test.dart

@@ -49,7 +49,7 @@ void main() {
 
     await tester.pumpWidget(MaterialApp(
       home: Center(
-        child: Container(
+        child: SizedBox(
           height: 300.0,
           child: ListView(
             controller: scrollController,
@@ -61,7 +61,7 @@ void main() {
                 style: textStyle,
                 cursorColor: cursorColor,
               ),
-              Container(
+              const SizedBox(
                 height: 350.0,
               ),
             ],
@@ -88,12 +88,12 @@ void main() {
 
     await tester.pumpWidget(MaterialApp(
       home: Center(
-        child: Container(
+        child: SizedBox(
           height: 300.0,
           child: ListView(
             controller: scrollController,
             children: <Widget>[
-              Container(
+              const SizedBox(
                 height: 200.0,
               ),
               EditableText(
@@ -104,7 +104,7 @@ void main() {
                 style: textStyle,
                 cursorColor: cursorColor,
               ),
-              Container(
+              const SizedBox(
                 height: 850.0,
               ),
             ],
@@ -134,12 +134,12 @@ void main() {
 
     await tester.pumpWidget(MaterialApp(
       home: Center(
-        child: Container(
+        child: SizedBox(
           height: 300.0,
           child: ListView(
             controller: scrollController,
             children: <Widget>[
-              Container(
+              const SizedBox(
                 height: 350.0,
               ),
               EditableText(
@@ -149,7 +149,7 @@ void main() {
                 style: textStyle,
                 cursorColor: cursorColor,
               ),
-              Container(
+              const SizedBox(
                 height: 350.0,
               ),
             ],
@@ -183,13 +183,13 @@ void main() {
 
     await tester.pumpWidget(MaterialApp(
       home: Center(
-        child: Container(
+        child: SizedBox(
           height: 300.0,
           child: ListView(
             physics: const NoImplicitScrollPhysics(),
             controller: scrollController,
             children: <Widget>[
-              Container(
+              const SizedBox(
                 height: 350.0,
               ),
               EditableText(
@@ -199,7 +199,7 @@ void main() {
                 style: textStyle,
                 cursorColor: cursorColor,
               ),
-              Container(
+              const SizedBox(
                 height: 350.0,
               ),
             ],
@@ -281,7 +281,7 @@ void main() {
 
     await tester.pumpWidget(MaterialApp(
       home: Center(
-        child: Container(
+        child: SizedBox(
           height: 300.0,
           child: ListView(
             controller: scrollController,
@@ -333,12 +333,12 @@ void main() {
     await tester.pumpWidget(MaterialApp(
       home: Align(
         alignment: Alignment.bottomCenter,
-        child: Container(
+        child: SizedBox(
           height: 300.0,
           child: ListView(
             controller: scrollController,
             children: <Widget>[
-              Container(
+              const SizedBox(
                 key: container,
                 height: 200.0,
               ),
@@ -350,7 +350,7 @@ void main() {
                 style: textStyle,
                 cursorColor: cursorColor,
               ),
-              Container(
+              const SizedBox(
                 height: 400.0,
               ),
             ],
@@ -406,7 +406,7 @@ void main() {
                     ),
                   )
                   : SliverToBoxAdapter(
-                    child: Container(
+                    child: SizedBox(
                       height: 100.0,
                       child: Text('Tile $i'),
                     ),
@@ -469,7 +469,7 @@ void main() {
                       ),
                     )
                     : SliverToBoxAdapter(
-                      child: Container(
+                      child: SizedBox(
                         height: 100.0,
                         child: Text('Tile $i'),
                       ),

packages/flutter/test/widgets/ensure_visible_test.dart

@@ -22,14 +22,14 @@ Widget buildSingleChildScrollView(Axis scrollDirection, { bool reverse = false }
           reverse: reverse,
           child: ListBody(
             mainAxis: scrollDirection,
-            children: <Widget>[
-              Container(key: const ValueKey<int>(0), width: 200.0, height: 200.0),
-              Container(key: const ValueKey<int>(1), width: 200.0, height: 200.0),
-              Container(key: const ValueKey<int>(2), width: 200.0, height: 200.0),
-              Container(key: const ValueKey<int>(3), width: 200.0, height: 200.0),
-              Container(key: const ValueKey<int>(4), width: 200.0, height: 200.0),
-              Container(key: const ValueKey<int>(5), width: 200.0, height: 200.0),
-              Container(key: const ValueKey<int>(6), width: 200.0, height: 200.0),
+            children: const <Widget>[
+              SizedBox(key: ValueKey<int>(0), width: 200.0, height: 200.0),
+              SizedBox(key: ValueKey<int>(1), width: 200.0, height: 200.0),
+              SizedBox(key: ValueKey<int>(2), width: 200.0, height: 200.0),
+              SizedBox(key: ValueKey<int>(3), width: 200.0, height: 200.0),
+              SizedBox(key: ValueKey<int>(4), width: 200.0, height: 200.0),
+              SizedBox(key: ValueKey<int>(5), width: 200.0, height: 200.0),
+              SizedBox(key: ValueKey<int>(6), width: 200.0, height: 200.0),
             ],
           ),
         ),
@@ -50,14 +50,14 @@ Widget buildListView(Axis scrollDirection, { bool reverse = false, bool shrinkWr
           reverse: reverse,
           addSemanticIndexes: false,
           shrinkWrap: shrinkWrap,
-          children: <Widget>[
-            Container(key: const ValueKey<int>(0), width: 200.0, height: 200.0),
-            Container(key: const ValueKey<int>(1), width: 200.0, height: 200.0),
-            Container(key: const ValueKey<int>(2), width: 200.0, height: 200.0),
-            Container(key: const ValueKey<int>(3), width: 200.0, height: 200.0),
-            Container(key: const ValueKey<int>(4), width: 200.0, height: 200.0),
-            Container(key: const ValueKey<int>(5), width: 200.0, height: 200.0),
-            Container(key: const ValueKey<int>(6), width: 200.0, height: 200.0),
+          children: const <Widget>[
+            SizedBox(key: ValueKey<int>(0), width: 200.0, height: 200.0),
+            SizedBox(key: ValueKey<int>(1), width: 200.0, height: 200.0),
+            SizedBox(key: ValueKey<int>(2), width: 200.0, height: 200.0),
+            SizedBox(key: ValueKey<int>(3), width: 200.0, height: 200.0),
+            SizedBox(key: ValueKey<int>(4), width: 200.0, height: 200.0),
+            SizedBox(key: ValueKey<int>(5), width: 200.0, height: 200.0),
+            SizedBox(key: ValueKey<int>(6), width: 200.0, height: 200.0),
           ],
         ),
       ),
@@ -187,10 +187,10 @@ void main() {
             child: SingleChildScrollView(
               child: ListBody(
                 children: <Widget>[
-                  Container(height: 200.0),
-                  Container(height: 200.0),
-                  Container(height: 200.0),
-                  Container(
+                  const SizedBox(height: 200.0),
+                  const SizedBox(height: 200.0),
+                  const SizedBox(height: 200.0),
+                  SizedBox(
                     height: 200.0,
                     child: Center(
                       child: Transform(
@@ -204,9 +204,9 @@ void main() {
                       ),
                     ),
                   ),
-                  Container(height: 200.0),
-                  Container(height: 200.0),
-                  Container(height: 200.0),
+                  const SizedBox(height: 200.0),
+                  const SizedBox(height: 200.0),
+                  const SizedBox(height: 200.0),
                 ],
               ),
             ),
@@ -230,9 +230,9 @@ void main() {
       final List<Row> rows = List<Row>.generate(
         7,
         (int y) => Row(
-          children: List<Container>.generate(
+          children: List<SizedBox>.generate(
             7,
-            (int x) => Container(key: ValueKey<String>('$x, $y'), width: 200.0, height: 200.0,),
+            (int x) => SizedBox(key: ValueKey<String>('$x, $y'), width: 200.0, height: 200.0,),
           ),
         ),
       );
@@ -519,10 +519,10 @@ void main() {
             height: 400.0,
             child: ListView(
               children: <Widget>[
-                Container(height: 200.0),
-                Container(height: 200.0),
-                Container(height: 200.0),
-                Container(
+                const SizedBox(height: 200.0),
+                const SizedBox(height: 200.0),
+                const SizedBox(height: 200.0),
+                SizedBox(
                   height: 200.0,
                   child: Center(
                     child: Transform(
@@ -536,9 +536,9 @@ void main() {
                     ),
                   ),
                 ),
-                Container(height: 200.0),
-                Container(height: 200.0),
-                Container(height: 200.0),
+                const SizedBox(height: 200.0),
+                const SizedBox(height: 200.0),
+                const SizedBox(height: 200.0),
               ],
             ),
           ),
@@ -722,20 +722,20 @@ void main() {
                   return Viewport(
                     offset: offset,
                     center: const ValueKey<String>('center'),
-                    slivers: <Widget>[
-                      SliverToBoxAdapter(child: Container(key: const ValueKey<int>(-6), width: 200.0, height: 200.0)),
-                      SliverToBoxAdapter(child: Container(key: const ValueKey<int>(-5), width: 200.0, height: 200.0)),
-                      SliverToBoxAdapter(child: Container(key: const ValueKey<int>(-4), width: 200.0, height: 200.0)),
-                      SliverToBoxAdapter(child: Container(key: const ValueKey<int>(-3), width: 200.0, height: 200.0)),
-                      SliverToBoxAdapter(child: Container(key: const ValueKey<int>(-2), width: 200.0, height: 200.0)),
-                      SliverToBoxAdapter(child: Container(key: const ValueKey<int>(-1), width: 200.0, height: 200.0)),
-                      SliverToBoxAdapter(child: Container(key: const ValueKey<int>(0), width: 200.0, height: 200.0), key: const ValueKey<String>('center')),
-                      SliverToBoxAdapter(child: Container(key: const ValueKey<int>(1), width: 200.0, height: 200.0)),
-                      SliverToBoxAdapter(child: Container(key: const ValueKey<int>(2), width: 200.0, height: 200.0)),
-                      SliverToBoxAdapter(child: Container(key: const ValueKey<int>(3), width: 200.0, height: 200.0)),
-                      SliverToBoxAdapter(child: Container(key: const ValueKey<int>(4), width: 200.0, height: 200.0)),
-                      SliverToBoxAdapter(child: Container(key: const ValueKey<int>(5), width: 200.0, height: 200.0)),
-                      SliverToBoxAdapter(child: Container(key: const ValueKey<int>(6), width: 200.0, height: 200.0)),
+                    slivers: const <Widget>[
+                      SliverToBoxAdapter(child: SizedBox(key: ValueKey<int>(-6), width: 200.0, height: 200.0)),
+                      SliverToBoxAdapter(child: SizedBox(key: ValueKey<int>(-5), width: 200.0, height: 200.0)),
+                      SliverToBoxAdapter(child: SizedBox(key: ValueKey<int>(-4), width: 200.0, height: 200.0)),
+                      SliverToBoxAdapter(child: SizedBox(key: ValueKey<int>(-3), width: 200.0, height: 200.0)),
+                      SliverToBoxAdapter(child: SizedBox(key: ValueKey<int>(-2), width: 200.0, height: 200.0)),
+                      SliverToBoxAdapter(child: SizedBox(key: ValueKey<int>(-1), width: 200.0, height: 200.0)),
+                      SliverToBoxAdapter(child: SizedBox(key: ValueKey<int>(0), width: 200.0, height: 200.0), key: ValueKey<String>('center')),
+                      SliverToBoxAdapter(child: SizedBox(key: ValueKey<int>(1), width: 200.0, height: 200.0)),
+                      SliverToBoxAdapter(child: SizedBox(key: ValueKey<int>(2), width: 200.0, height: 200.0)),
+                      SliverToBoxAdapter(child: SizedBox(key: ValueKey<int>(3), width: 200.0, height: 200.0)),
+                      SliverToBoxAdapter(child: SizedBox(key: ValueKey<int>(4), width: 200.0, height: 200.0)),
+                      SliverToBoxAdapter(child: SizedBox(key: ValueKey<int>(5), width: 200.0, height: 200.0)),
+                      SliverToBoxAdapter(child: SizedBox(key: ValueKey<int>(6), width: 200.0, height: 200.0)),
                     ],
                   );
                 },

packages/flutter/test/widgets/fitted_box_test.dart

@@ -13,11 +13,11 @@ void main() {
 
     await tester.pumpWidget(
       Center(
-        child: Container(
+        child: SizedBox(
           width: 200.0,
           child: FittedBox(
             key: outside,
-            child: Container(
+            child: SizedBox(
               key: inside,
               width: 100.0,
               height: 50.0,
@@ -48,12 +48,12 @@ void main() {
 
     await tester.pumpWidget(
       Center(
-        child: Container(
+        child: SizedBox(
           width: 200.0,
           height: 200.0,
           child: FittedBox(
             key: outside,
-            child: Container(
+            child: SizedBox(
               key: inside,
               width: 100.0,
               height: 50.0,
@@ -83,13 +83,13 @@ void main() {
 
     await tester.pumpWidget(
       Center(
-        child: Container(
+        child: SizedBox(
           width: 200.0,
           height: 200.0,
           child: FittedBox(
             key: outside,
             fit: BoxFit.cover,
-            child: Container(
+            child: SizedBox(
               key: inside,
               width: 100.0,
               height: 50.0,
@@ -139,14 +139,14 @@ void main() {
         Directionality(
           textDirection: TextDirection.rtl,
           child: Center(
-            child: Container(
+            child: SizedBox(
               width: 100.0,
               height: 100.0,
               child: FittedBox(
                 key: outside,
                 fit: BoxFit.scaleDown,
                 alignment: AlignmentDirectional.bottomEnd,
-                child: Container(
+                child: SizedBox(
                   key: inside,
                   width: 10.0,
                   height: 10.0,
@@ -180,14 +180,14 @@ void main() {
         Directionality(
           textDirection: TextDirection.ltr,
           child: Center(
-            child: Container(
+            child: SizedBox(
               width: 100.0,
               height: 100.0,
               child: FittedBox(
                 key: outside,
                 fit: BoxFit.scaleDown,
                 alignment: AlignmentDirectional.bottomEnd,
-                child: Container(
+                child: SizedBox(
                   key: inside,
                   width: 10.0,
                   height: 10.0,
@@ -221,14 +221,14 @@ void main() {
         Directionality(
           textDirection: TextDirection.ltr,
           child: Center(
-            child: Container(
+            child: SizedBox(
               width: 100.0,
               height: 100.0,
               child: FittedBox(
                 key: outside,
                 fit: BoxFit.scaleDown,
                 alignment: AlignmentDirectional.center,
-                child: Container(
+                child: SizedBox(
                   key: inside,
                   width: 10.0,
                   height: 10.0,
@@ -262,14 +262,14 @@ void main() {
         Directionality(
           textDirection: TextDirection.ltr,
           child: Center(
-            child: Container(
+            child: SizedBox(
               width: 100.0,
               height: 100.0,
               child: FittedBox(
                 key: outside,
                 fit: BoxFit.scaleDown,
                 alignment: AlignmentDirectional.center,
-                child: Container(
+                child: SizedBox(
                   key: inside,
                   width: 30.0,
                   height: 10.0,
@@ -303,14 +303,14 @@ void main() {
         Directionality(
           textDirection: TextDirection.ltr,
           child: Center(
-            child: Container(
+            child: SizedBox(
               width: 100.0,
               height: 100.0,
               child: FittedBox(
                 key: outside,
                 fit: BoxFit.fill,
                 alignment: AlignmentDirectional.center,
-                child: Container(
+                child: SizedBox(
                   key: inside,
                   width: 30.0,
                   height: 10.0,
@@ -493,12 +493,12 @@ void main() {
 
     await tester.pumpWidget(
       Center(
-        child: Container(
+        child: SizedBox(
           width: 200.0,
           child: FittedBox(
             key: outside,
             fit: BoxFit.scaleDown,
-            child: Container(
+            child: SizedBox(
               key: inside,
               width: 100.0,
               height: 50.0,
@@ -522,12 +522,12 @@ void main() {
 
     await tester.pumpWidget(
       Center(
-        child: Container(
+        child: SizedBox(
           width: 200.0,
           child: FittedBox(
             key: outside,
             fit: BoxFit.scaleDown,
-            child: Container(
+            child: SizedBox(
               key: inside,
               width: 400.0,
               height: 200.0,
@@ -550,12 +550,12 @@ void main() {
     final Key outside = UniqueKey();
 
     final Widget scaleDownWidget = Center(
-      child: Container(
+      child: SizedBox(
         width: 200.0,
         child: FittedBox(
           key: outside,
           fit: BoxFit.scaleDown,
-          child: Container(
+          child: const SizedBox(
             width: 100.0,
             height: 50.0,
           ),
@@ -564,11 +564,11 @@ void main() {
     );
 
     final Widget coverWidget = Center(
-      child: Container(
+      child: SizedBox(
         width: 200.0,
         child: FittedBox(
           key: outside,
-          child: Container(
+          child: const SizedBox(
             width: 100.0,
             height: 50.0,
           ),

packages/flutter/test/widgets/flex_test.dart

@@ -65,16 +65,16 @@ void main() {
     // both of these cases have failed in the past due to floating point issues
     await tester.pumpWidget(
       Center(
-        child: Container(
+        child: SizedBox(
           height: 400.0,
           child: Column(
-            children: <Widget>[
-              Expanded(child: Container()),
-              Expanded(child: Container()),
-              Expanded(child: Container()),
-              Expanded(child: Container()),
-              Expanded(child: Container()),
-              Expanded(child: Container()),
+            children: const <Widget>[
+              Expanded(child: SizedBox()),
+              Expanded(child: SizedBox()),
+              Expanded(child: SizedBox()),
+              Expanded(child: SizedBox()),
+              Expanded(child: SizedBox()),
+              Expanded(child: SizedBox()),
             ],
           ),
         ),
@@ -82,16 +82,16 @@ void main() {
     );
     await tester.pumpWidget(
       Center(
-        child: Container(
+        child: SizedBox(
           height: 199.0,
           child: Column(
-            children: <Widget>[
-              Expanded(child: Container()),
-              Expanded(child: Container()),
-              Expanded(child: Container()),
-              Expanded(child: Container()),
-              Expanded(child: Container()),
-              Expanded(child: Container()),
+            children: const <Widget>[
+              Expanded(child: SizedBox()),
+              Expanded(child: SizedBox()),
+              Expanded(child: SizedBox()),
+              Expanded(child: SizedBox()),
+              Expanded(child: SizedBox()),
+              Expanded(child: SizedBox()),
             ],
           ),
         ),

packages/flutter/test/widgets/focus_manager_test.dart

@@ -74,14 +74,14 @@ void main() {
           padding: const EdgeInsets.all(8.0),
           child: Column(
             children: <Widget>[
-              Focus(focusNode: focusNode1, child: Container(width: 200, height: 100),),
+              Focus(focusNode: focusNode1, child: const SizedBox(width: 200, height: 100),),
               Transform.translate(
                 offset: const Offset(10, 20),
                 child: Transform.scale(
                   scale: 0.33,
                   child: Transform.rotate(
                     angle: math.pi,
-                    child: Focus(focusNode: focusNode2, child: Container(width: 200, height: 100)),
+                    child: Focus(focusNode: focusNode2, child: const SizedBox(width: 200, height: 100)),
                   ),
                 ),
               ),

packages/flutter/test/widgets/focus_traversal_test.dart

@@ -38,11 +38,11 @@ void main() {
             children: <Widget>[
               Focus(
                 key: key2,
-                child: Container(key: key3, width: 100, height: 100),
+                child: SizedBox(key: key3, width: 100, height: 100),
               ),
               Focus(
                 key: key4,
-                child: Container(key: key5, width: 100, height: 100),
+                child: SizedBox(key: key5, width: 100, height: 100),
               ),
             ],
           ),
@@ -77,11 +77,11 @@ void main() {
             children: <Widget>[
               Focus(
                 key: key2,
-                child: Container(key: key3, width: 100, height: 100),
+                child: SizedBox(key: key3, width: 100, height: 100),
               ),
               Focus(
                 key: key4,
-                child: Container(key: key5, width: 100, height: 100),
+                child: SizedBox(key: key5, width: 100, height: 100),
               ),
             ],
           ),
@@ -413,11 +413,11 @@ void main() {
             children: <Widget>[
               Focus(
                 key: key2,
-                child: Container(key: key3, width: 100, height: 100),
+                child: SizedBox(key: key3, width: 100, height: 100),
               ),
               Focus(
                 key: key4,
-                child: Container(key: key5, width: 100, height: 100),
+                child: SizedBox(key: key5, width: 100, height: 100),
               ),
             ],
           ),
@@ -849,13 +849,13 @@ void main() {
               FocusTraversalOrder(
                 order: const NumericFocusOrder(2),
                 child: Focus(
-                  child: Container(key: key1, width: 100, height: 100),
+                  child: SizedBox(key: key1, width: 100, height: 100),
                 ),
               ),
               FocusTraversalOrder(
                 order: const NumericFocusOrder(1),
                 child: Focus(
-                  child: Container(key: key2, width: 100, height: 100),
+                  child: SizedBox(key: key2, width: 100, height: 100),
                 ),
               ),
             ],
@@ -1225,12 +1225,12 @@ void main() {
                       Focus(
                         debugLabel: 'upperLeft',
                         onFocusChange: (bool focus) => focusUpperLeft = focus,
-                        child: Container(width: 100, height: 100, key: upperLeftKey),
+                        child: SizedBox(width: 100, height: 100, key: upperLeftKey),
                       ),
                       Focus(
                         debugLabel: 'upperRight',
                         onFocusChange: (bool focus) => focusUpperRight = focus,
-                        child: Container(width: 100, height: 100, key: upperRightKey),
+                        child: SizedBox(width: 100, height: 100, key: upperRightKey),
                       ),
                     ],
                   ),
@@ -1239,12 +1239,12 @@ void main() {
                       Focus(
                         debugLabel: 'lowerLeft',
                         onFocusChange: (bool focus) => focusLowerLeft = focus,
-                        child: Container(width: 100, height: 100, key: lowerLeftKey),
+                        child: SizedBox(width: 100, height: 100, key: lowerLeftKey),
                       ),
                       Focus(
                         debugLabel: 'lowerRight',
                         onFocusChange: (bool focus) => focusLowerRight = focus,
-                        child: Container(width: 100, height: 100, key: lowerRightKey),
+                        child: SizedBox(width: 100, height: 100, key: lowerRightKey),
                       ),
                     ],
                   ),
@@ -1356,7 +1356,7 @@ void main() {
         return Focus(
           debugLabel: keys[index].toString(),
           onFocusChange: (bool isFocused) => focus[index] = isFocused,
-          child: Container(width: 100, height: 100, key: keys[index]),
+          child: SizedBox(width: 100, height: 100, key: keys[index]),
         );
       }
 
@@ -1498,11 +1498,11 @@ void main() {
                     children: <Widget>[
                       Focus(
                         debugLabel: 'upperLeft',
-                        child: Container(width: 100, height: 100, key: upperLeftKey),
+                        child: SizedBox(width: 100, height: 100, key: upperLeftKey),
                       ),
                       Focus(
                         debugLabel: 'upperRight',
-                        child: Container(width: 100, height: 100, key: upperRightKey),
+                        child: SizedBox(width: 100, height: 100, key: upperRightKey),
                       ),
                     ],
                   ),
@@ -1510,7 +1510,7 @@ void main() {
                     children: <Widget>[
                       Focus(
                         debugLabel: 'lowerLeft',
-                        child: Container(width: 100, height: 100, key: lowerLeftKey),
+                        child: SizedBox(width: 100, height: 100, key: lowerLeftKey),
                       ),
                       const Focus(
                         debugLabel: 'lowerRight',
@@ -1613,11 +1613,11 @@ void main() {
                           Focus(
                             autofocus: true,
                             debugLabel: 'upperLeft',
-                            child: Container(width: 100, height: 100, key: upperLeftKey),
+                            child: SizedBox(width: 100, height: 100, key: upperLeftKey),
                           ),
                           Focus(
                             debugLabel: 'upperRight',
-                            child: Container(width: 100, height: 100, key: upperRightKey),
+                            child: SizedBox(width: 100, height: 100, key: upperRightKey),
                           ),
                         ],
                       ),
@@ -1625,11 +1625,11 @@ void main() {
                         children: <Widget>[
                           Focus(
                             debugLabel: 'lowerLeft',
-                            child: Container(width: 100, height: 100, key: lowerLeftKey),
+                            child: SizedBox(width: 100, height: 100, key: lowerLeftKey),
                           ),
                           Focus(
                             debugLabel: 'lowerRight',
-                            child: Container(width: 100, height: 100, key: lowerRightKey),
+                            child: SizedBox(width: 100, height: 100, key: lowerRightKey),
                           ),
                         ],
                       ),
@@ -1909,7 +1909,7 @@ void main() {
                 children: <Widget>[
                   Row(
                     children: <Widget>[
-                      Container(
+                      SizedBox(
                         width: 100,
                         height: 100,
                         child: EditableText(
@@ -1922,7 +1922,7 @@ void main() {
                           style: const TextStyle(),
                         ),
                       ),
-                      Container(
+                      SizedBox(
                         width: 100,
                         height: 100,
                         child: EditableText(
@@ -1938,7 +1938,7 @@ void main() {
                   ),
                   Row(
                     children: <Widget>[
-                      Container(
+                      SizedBox(
                         width: 100,
                         height: 100,
                         child: EditableText(
@@ -1950,7 +1950,7 @@ void main() {
                           style: const TextStyle(),
                         ),
                       ),
-                      Container(
+                      SizedBox(
                         width: 100,
                         height: 100,
                         child: EditableText(

packages/flutter/test/widgets/framework_test.dart

@@ -1030,7 +1030,7 @@ void main() {
     await tester.pumpWidget(Directionality(
       textDirection: TextDirection.ltr,
       child: Center(
-        child: Container(
+        child: SizedBox(
           height: 100,
           child: CustomScrollView(
             controller: ScrollController(),

packages/flutter/test/widgets/gesture_detector_test.dart

@@ -155,7 +155,7 @@ void main() {
                     color: const Color(0xFF00FF00),
                   ),
                 ),
-                Container(
+                SizedBox(
                   width: 100.0,
                   height: 100.0,
                   child: GestureDetector(

packages/flutter/test/widgets/grid_view_layout_test.dart

@@ -18,7 +18,7 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             width: 200.0,
             child: GridView.extent(
               maxCrossAxisExtent: 100.0,
@@ -47,7 +47,7 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             width: 200.0,
             child: GridView.extent(
               maxCrossAxisExtent: 60.0,

packages/flutter/test/widgets/heroes_test.dart

@@ -43,7 +43,7 @@ final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
         Card(child: Hero(
           tag: 'a',
           transitionOnUserGestures: transitionFromUserGestures,
-          child: Container(height: 100.0, width: 100.0, key: firstKey),
+          child: SizedBox(height: 100.0, width: 100.0, key: firstKey),
         )),
         const SizedBox(height: 100.0, width: 100.0),
         TextButton(
@@ -73,7 +73,7 @@ final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
         Card(child: Hero(
           tag: 'a',
           transitionOnUserGestures: transitionFromUserGestures,
-          child: Container(height: 150.0, width: 150.0, key: secondKey),
+          child: SizedBox(height: 150.0, width: 150.0, key: secondKey),
         )),
         const SizedBox(height: 150.0, width: 150.0),
         TextButton(
@@ -102,7 +102,7 @@ final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
             child: Hero(
               tag: 'a',
               transitionOnUserGestures: transitionFromUserGestures,
-              child: Container(height: 150.0, width: 150.0, key: secondKey),
+              child: SizedBox(height: 150.0, width: 150.0, key: secondKey),
             ),
           ),
         ),
@@ -123,7 +123,7 @@ final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
       child: Hero(
         tag: 'a',
         transitionOnUserGestures: transitionFromUserGestures,
-        child: Container(height: 150.0, width: 150.0, key: simpleKey),
+        child: SizedBox(height: 150.0, width: 150.0, key: simpleKey),
       ),
     ),
   ),
@@ -137,7 +137,7 @@ class ThreeRoute extends MaterialPageRoute<void> {
           child: ListView(
             children: <Widget>[
               const SizedBox(height: 200.0, width: 200.0),
-              Card(child: Hero(tag: 'a', child: Container(height: 200.0, width: 200.0, key: thirdKey))),
+              Card(child: Hero(tag: 'a', child: SizedBox(height: 200.0, width: 200.0, key: thirdKey))),
               const SizedBox(height: 200.0, width: 200.0),
             ],
           ),
@@ -497,10 +497,10 @@ Future<void> main() async {
             onTap: () {
               log.add('foo');
             },
-            child: Container(
+            child: const SizedBox(
               width: 100.0,
               height: 100.0,
-              child: const Text('foo'),
+              child: Text('foo'),
             ),
           ),
         ),
@@ -515,10 +515,10 @@ Future<void> main() async {
                 onTap: () {
                   log.add('bar');
                 },
-                child: Container(
+                child: const SizedBox(
                   width: 100.0,
                   height: 150.0,
-                  child: const Text('bar'),
+                  child: Text('bar'),
                 ),
               ),
             ),
@@ -813,7 +813,7 @@ Future<void> main() async {
                   heroCardSetState = setState;
                   return Card(
                     child: routeIncludesHero
-                      ? Hero(tag: 'H', child: Container(key: routeHeroKey, height: 200.0, width: 200.0))
+                      ? const Hero(tag: 'H', child: SizedBox(key: routeHeroKey, height: 200.0, width: 200.0))
                       : const SizedBox(height: 200.0, width: 200.0),
                   );
                 },
@@ -836,8 +836,8 @@ Future<void> main() async {
             builder: (BuildContext context) { // Navigator.push() needs context
               return ListView(
                 children: <Widget> [
-                  Card(
-                    child: Hero(tag: 'H', child: Container(key: homeHeroKey, height: 100.0, width: 100.0)),
+                  const Card(
+                    child: Hero(tag: 'H', child: SizedBox(key: homeHeroKey, height: 100.0, width: 100.0)),
                   ),
                   TextButton(
                     child: const Text('PUSH'),
@@ -914,7 +914,7 @@ Future<void> main() async {
               // This container will appear at Y=100
               Container(
                 key: routeContainerKey,
-                child: Hero(tag: 'H', child: Container(key: routeHeroKey, height: 200.0, width: 200.0)),
+                child: const Hero(tag: 'H', child: SizedBox(key: routeHeroKey, height: 200.0, width: 200.0)),
               ),
               TextButton(
                 child: const Text('POP'),
@@ -945,7 +945,7 @@ Future<void> main() async {
                   const SizedBox(height: 200.0),
                   // This container will appear at Y=200
                   Container(
-                    child: Hero(tag: 'H', child: Container(key: homeHeroKey, height: 100.0, width: 100.0)),
+                    child: const Hero(tag: 'H', child: SizedBox(key: homeHeroKey, height: 100.0, width: 100.0)),
                   ),
                   TextButton(
                     child: const Text('PUSH'),
@@ -1004,7 +1004,7 @@ Future<void> main() async {
               // This container will appear at Y=100
               Container(
                 key: routeContainerKey,
-                child: Hero(tag: 'H', child: Container(key: routeHeroKey, height: 200.0, width: 200.0)),
+                child: const Hero(tag: 'H', child: SizedBox(key: routeHeroKey, height: 200.0, width: 200.0)),
               ),
               const SizedBox(height: 800.0),
             ],
@@ -1024,7 +1024,7 @@ Future<void> main() async {
                   const SizedBox(height: 200.0),
                   // This container will appear at Y=200
                   Container(
-                    child: Hero(tag: 'H', child: Container(key: homeHeroKey, height: 100.0, width: 100.0)),
+                    child: const Hero(tag: 'H', child: SizedBox(key: homeHeroKey, height: 100.0, width: 100.0)),
                   ),
                   TextButton(
                     child: const Text('PUSH'),
@@ -1080,12 +1080,12 @@ Future<void> main() async {
             children: <Widget>[
               // This container will appear at Y=0
               Container(
-                child: Hero(
+                child: const Hero(
                   tag: 'BC',
-                  child: Container(
+                  child: SizedBox(
                     key: heroBCKey,
                     height: 150.0,
-                    child: const Text('Hero'),
+                    child: Text('Hero'),
                   ),
                 ),
               ),
@@ -1105,12 +1105,12 @@ Future<void> main() async {
               const SizedBox(height: 100.0),
               // This container will appear at Y=100
               Container(
-                child: Hero(
+                child: const Hero(
                   tag: 'AB',
-                  child: Container(
+                  child: SizedBox(
                     key: heroABKey,
                     height: 200.0,
-                    child: const Text('Hero'),
+                    child: Text('Hero'),
                   ),
                 ),
               ),
@@ -1119,11 +1119,11 @@ Future<void> main() async {
                 onPressed: () { Navigator.push(context, routeC); },
               ),
               Container(
-                child: Hero(
+                child: const Hero(
                   tag: 'BC',
-                  child: Container(
+                  child: SizedBox(
                     height: 150.0,
-                    child: const Text('Hero'),
+                    child: Text('Hero'),
                   ),
                 ),
               ),
@@ -1145,12 +1145,12 @@ Future<void> main() async {
                   const SizedBox(height: 200.0),
                   // This container will appear at Y=200
                   Container(
-                    child: Hero(
+                    child: const Hero(
                       tag: 'AB',
-                      child: Container(
+                      child: SizedBox(
                         height: 100.0,
                         width: 100.0,
-                        child: const Text('Hero'),
+                        child: Text('Hero'),
                       ),
                     ),
                   ),
@@ -1309,7 +1309,7 @@ Future<void> main() async {
             Hero(
               tag: 'a',
               createRectTween: createRectTween,
-              child: Container(height: 100.0, width: 100.0, key: firstKey),
+              child: SizedBox(height: 100.0, width: 100.0, key: firstKey),
             ),
             TextButton(
               child: const Text('two'),
@@ -1332,7 +1332,7 @@ Future<void> main() async {
             Hero(
               tag: 'a',
               createRectTween: createRectTween,
-              child: Container(height: 200.0, width: 100.0, key: secondKey),
+              child: SizedBox(height: 200.0, width: 100.0, key: secondKey),
             ),
           ],
         ),
@@ -1424,7 +1424,7 @@ Future<void> main() async {
             Hero(
               tag: 'a',
               createRectTween: createRectTween,
-              child: Container(height: 100.0, width: 100.0, key: firstKey),
+              child: SizedBox(height: 100.0, width: 100.0, key: firstKey),
             ),
             TextButton(
               child: const Text('two'),
@@ -1447,7 +1447,7 @@ Future<void> main() async {
             Hero(
               tag: 'a',
               createRectTween: createRectTween,
-              child: Container(height: 200.0, width: 100.0, key: secondKey),
+              child: SizedBox(height: 200.0, width: 100.0, key: secondKey),
             ),
           ],
         ),
@@ -2402,7 +2402,7 @@ Future<void> main() async {
               Hero(
                 tag: 'hero',
                 transitionOnUserGestures: true,
-                child: Container(
+                child: SizedBox(
                   width: 100,
                   child: Image(
                     image: imageProvider,
@@ -2572,7 +2572,7 @@ Future<void> main() async {
               createRectTween: (Rect? begin, Rect? end) {
                 return RectTween(begin: begin, end: end);
               },
-              child: Container(
+              child: SizedBox(
                 key: container1,
                 height: 100,
                 width: 100,
@@ -2593,7 +2593,7 @@ Future<void> main() async {
             createRectTween: (Rect? begin, Rect? end) {
               return RectTween(begin: begin, end: end);
             },
-            child: Container(
+            child: SizedBox(
               key: container2,
               height: 200,
               width: 200,

packages/flutter/test/widgets/image_resolution_test.dart

@@ -137,7 +137,7 @@ Widget buildImageAtRatio(String imageName, Key key, double ratio, bool inferSize
 Widget buildImageCacheResized(String name, Key key, int width, int height, int cacheWidth, int cacheHeight) {
   return Center(
     child: RepaintBoundary(
-      child: Container(
+      child: SizedBox(
         width: 250,
         height: 250,
         child: Center(

packages/flutter/test/widgets/image_rtl_test.dart

@@ -298,7 +298,7 @@ void main() {
       Directionality(
         textDirection: TextDirection.rtl,
         child: Center(
-          child: Container(
+          child: SizedBox(
             width: 100.0,
             height: 50.0,
             child: Image(
@@ -313,7 +313,7 @@ void main() {
       Duration.zero,
       EnginePhase.layout, // so that we don't try to paint the fake images
     );
-    expect(find.byType(Container), paints
+    expect(find.byType(SizedBox), paints
       ..clipRect(rect: const Rect.fromLTRB(0.0, 0.0, 100.0, 50.0))
       ..translate(x: 50.0, y: 0.0)
       ..scale(x: -1.0, y: 1.0)
@@ -327,7 +327,7 @@ void main() {
       ..drawImageRect(source: const Rect.fromLTRB(0.0, 0.0, 16.0, 9.0), destination: const Rect.fromLTRB(84.0, 0.0, 100.0, 9.0))
       ..restore(),
     );
-    expect(find.byType(Container), isNot(paints..scale()..scale()));
+    expect(find.byType(SizedBox), isNot(paints..scale()..scale()));
   });
 
   testWidgets('Image LTR with alignment topEnd (and pointless match)', (WidgetTester tester) async {
@@ -335,7 +335,7 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             width: 100.0,
             height: 50.0,
             child: Image(
@@ -350,7 +350,7 @@ void main() {
       Duration.zero,
       EnginePhase.layout, // so that we don't try to paint the fake images
     );
-    expect(find.byType(Container), paints
+    expect(find.byType(SizedBox), paints
       ..clipRect(rect: const Rect.fromLTRB(0.0, 0.0, 100.0, 50.0))
       ..drawImageRect(source: const Rect.fromLTRB(0.0, 0.0, 16.0, 9.0), destination: const Rect.fromLTRB(-12.0, 0.0, 4.0, 9.0))
       ..drawImageRect(source: const Rect.fromLTRB(0.0, 0.0, 16.0, 9.0), destination: const Rect.fromLTRB(4.0, 0.0, 20.0, 9.0))
@@ -361,7 +361,7 @@ void main() {
       ..drawImageRect(source: const Rect.fromLTRB(0.0, 0.0, 16.0, 9.0), destination: const Rect.fromLTRB(84.0, 0.0, 100.0, 9.0))
       ..restore(),
     );
-    expect(find.byType(Container), isNot(paints..scale()));
+    expect(find.byType(SizedBox), isNot(paints..scale()));
   });
 
   testWidgets('Image RTL with alignment topEnd', (WidgetTester tester) async {
@@ -369,7 +369,7 @@ void main() {
       Directionality(
         textDirection: TextDirection.rtl,
         child: Center(
-          child: Container(
+          child: SizedBox(
             width: 100.0,
             height: 50.0,
             child: Image(
@@ -383,7 +383,7 @@ void main() {
       Duration.zero,
       EnginePhase.layout, // so that we don't try to paint the fake images
     );
-    expect(find.byType(Container), paints
+    expect(find.byType(SizedBox), paints
       ..clipRect(rect: const Rect.fromLTRB(0.0, 0.0, 100.0, 50.0))
       ..drawImageRect(source: const Rect.fromLTRB(0.0, 0.0, 16.0, 9.0), destination: const Rect.fromLTRB(0.0, 0.0, 16.0, 9.0))
       ..drawImageRect(source: const Rect.fromLTRB(0.0, 0.0, 16.0, 9.0), destination: const Rect.fromLTRB(16.0, 0.0, 32.0, 9.0))
@@ -394,7 +394,7 @@ void main() {
       ..drawImageRect(source: const Rect.fromLTRB(0.0, 0.0, 16.0, 9.0), destination: const Rect.fromLTRB(96.0, 0.0, 112.0, 9.0))
       ..restore(),
     );
-    expect(find.byType(Container), isNot(paints..scale()));
+    expect(find.byType(SizedBox), isNot(paints..scale()));
   });
 
   testWidgets('Image LTR with alignment topEnd', (WidgetTester tester) async {
@@ -402,7 +402,7 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             width: 100.0,
             height: 50.0,
             child: Image(
@@ -416,7 +416,7 @@ void main() {
       Duration.zero,
       EnginePhase.layout, // so that we don't try to paint the fake images
     );
-    expect(find.byType(Container), paints
+    expect(find.byType(SizedBox), paints
       ..clipRect(rect: const Rect.fromLTRB(0.0, 0.0, 100.0, 50.0))
       ..drawImageRect(source: const Rect.fromLTRB(0.0, 0.0, 16.0, 9.0), destination: const Rect.fromLTRB(-12.0, 0.0, 4.0, 9.0))
       ..drawImageRect(source: const Rect.fromLTRB(0.0, 0.0, 16.0, 9.0), destination: const Rect.fromLTRB(4.0, 0.0, 20.0, 9.0))
@@ -427,7 +427,7 @@ void main() {
       ..drawImageRect(source: const Rect.fromLTRB(0.0, 0.0, 16.0, 9.0), destination: const Rect.fromLTRB(84.0, 0.0, 100.0, 9.0))
       ..restore(),
     );
-    expect(find.byType(Container), isNot(paints..scale()));
+    expect(find.byType(SizedBox), isNot(paints..scale()));
   });
 
   testWidgets('Image RTL with alignment center-right and match', (WidgetTester tester) async {
@@ -435,7 +435,7 @@ void main() {
       Directionality(
         textDirection: TextDirection.rtl,
         child: Center(
-          child: Container(
+          child: SizedBox(
             width: 100.0,
             height: 50.0,
             child: Image(
@@ -447,15 +447,15 @@ void main() {
         ),
       ),
     );
-    expect(find.byType(Container), paints
+    expect(find.byType(SizedBox), paints
       ..translate(x: 50.0, y: 0.0)
       ..scale(x: -1.0, y: 1.0)
       ..translate(x: -50.0, y: 0.0)
       ..drawImageRect(source: const Rect.fromLTRB(0.0, 0.0, 16.0, 9.0), destination: const Rect.fromLTRB(0.0, 20.5, 16.0, 29.5))
       ..restore(),
     );
-    expect(find.byType(Container), isNot(paints..scale()..scale()));
-    expect(find.byType(Container), isNot(paints..drawImageRect()..drawImageRect()));
+    expect(find.byType(SizedBox), isNot(paints..scale()..scale()));
+    expect(find.byType(SizedBox), isNot(paints..drawImageRect()..drawImageRect()));
   });
 
   testWidgets('Image RTL with alignment center-right and no match', (WidgetTester tester) async {
@@ -463,7 +463,7 @@ void main() {
       Directionality(
         textDirection: TextDirection.rtl,
         child: Center(
-          child: Container(
+          child: SizedBox(
             width: 100.0,
             height: 50.0,
             child: Image(
@@ -476,11 +476,11 @@ void main() {
       Duration.zero,
       EnginePhase.layout, // so that we don't try to paint the fake images
     );
-    expect(find.byType(Container), paints
+    expect(find.byType(SizedBox), paints
       ..drawImageRect(source: const Rect.fromLTRB(0.0, 0.0, 16.0, 9.0), destination: const Rect.fromLTRB(84.0, 20.5, 100.0, 29.5)),
     );
-    expect(find.byType(Container), isNot(paints..scale()));
-    expect(find.byType(Container), isNot(paints..drawImageRect()..drawImageRect()));
+    expect(find.byType(SizedBox), isNot(paints..scale()));
+    expect(find.byType(SizedBox), isNot(paints..drawImageRect()..drawImageRect()));
   });
 
   testWidgets('Image LTR with alignment center-right and match', (WidgetTester tester) async {
@@ -488,7 +488,7 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             width: 100.0,
             height: 50.0,
             child: Image(
@@ -502,11 +502,11 @@ void main() {
       Duration.zero,
       EnginePhase.layout, // so that we don't try to paint the fake images
     );
-    expect(find.byType(Container), paints
+    expect(find.byType(SizedBox), paints
       ..drawImageRect(source: const Rect.fromLTRB(0.0, 0.0, 16.0, 9.0), destination: const Rect.fromLTRB(84.0, 20.5, 100.0, 29.5)),
     );
-    expect(find.byType(Container), isNot(paints..scale()));
-    expect(find.byType(Container), isNot(paints..drawImageRect()..drawImageRect()));
+    expect(find.byType(SizedBox), isNot(paints..scale()));
+    expect(find.byType(SizedBox), isNot(paints..drawImageRect()..drawImageRect()));
   });
 
   testWidgets('Image LTR with alignment center-right and no match', (WidgetTester tester) async {
@@ -514,7 +514,7 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             width: 100.0,
             height: 50.0,
             child: Image(
@@ -528,11 +528,11 @@ void main() {
       Duration.zero,
       EnginePhase.layout, // so that we don't try to paint the fake images
     );
-    expect(find.byType(Container), paints
+    expect(find.byType(SizedBox), paints
       ..drawImageRect(source: const Rect.fromLTRB(0.0, 0.0, 16.0, 9.0), destination: const Rect.fromLTRB(84.0, 20.5, 100.0, 29.5)),
     );
-    expect(find.byType(Container), isNot(paints..scale()));
-    expect(find.byType(Container), isNot(paints..drawImageRect()..drawImageRect()));
+    expect(find.byType(SizedBox), isNot(paints..scale()));
+    expect(find.byType(SizedBox), isNot(paints..drawImageRect()..drawImageRect()));
   });
 
   testWidgets('Image - Switch needing direction', (WidgetTester tester) async {

packages/flutter/test/widgets/implicit_animations_test.dart

@@ -547,7 +547,7 @@ class _TestTweenAnimationBuilderWidgetState extends _TestAnimatedWidgetState {
       duration: duration,
       onEnd: widget.callback,
       builder: (BuildContext context, double? size, Widget? child) {
-        return Container(
+        return SizedBox(
           child: child,
           width: size,
           height: size,

packages/flutter/test/widgets/interactive_viewer_test.dart

@@ -20,7 +20,7 @@ void main() {
             body: Center(
               child: InteractiveViewer(
                 transformationController: transformationController,
-                child: Container(width: 200.0, height: 200.0),
+                child: const SizedBox(width: 200.0, height: 200.0),
               ),
             ),
           ),
@@ -31,7 +31,7 @@ void main() {
 
       // Attempting to drag to pan doesn't work because the child fits inside
       // the viewport and has a tight boundary.
-      final Offset childOffset = tester.getTopLeft(find.byType(Container));
+      final Offset childOffset = tester.getTopLeft(find.byType(SizedBox));
       final Offset childInterior = Offset(
         childOffset.dx + 20.0,
         childOffset.dy + 20.0,
@@ -76,7 +76,7 @@ void main() {
                 boundaryMargin: const EdgeInsets.all(boundaryMargin),
                 minScale: minScale,
                 transformationController: transformationController,
-                child: Container(width: 200.0, height: 200.0),
+                child: const SizedBox(width: 200.0, height: 200.0),
               ),
             ),
           ),
@@ -86,7 +86,7 @@ void main() {
       expect(transformationController.value, equals(Matrix4.identity()));
 
       // Dragging to pan works only until it hits the boundary.
-      final Offset childOffset = tester.getTopLeft(find.byType(Container));
+      final Offset childOffset = tester.getTopLeft(find.byType(SizedBox));
       final Offset childInterior = Offset(
         childOffset.dx + 20.0,
         childOffset.dy + 20.0,
@@ -133,7 +133,7 @@ void main() {
                 constrained: false,
                 scaleEnabled: false,
                 transformationController: transformationController,
-                child: Container(width: 2000.0, height: 2000.0),
+                child: const SizedBox(width: 2000.0, height: 2000.0),
               ),
             ),
           ),
@@ -143,7 +143,7 @@ void main() {
       expect(transformationController.value, equals(Matrix4.identity()));
 
       // Attempting to move against the boundary doesn't work.
-      final Offset childOffset = tester.getTopLeft(find.byType(Container));
+      final Offset childOffset = tester.getTopLeft(find.byType(SizedBox));
       final Offset childInterior = Offset(
         childOffset.dx + 20.0,
         childOffset.dy + 20.0,
@@ -211,7 +211,7 @@ void main() {
                 boundaryMargin: const EdgeInsets.all(double.infinity),
                 minScale: minScale,
                 transformationController: transformationController,
-                child: Container(width: 200.0, height: 200.0),
+                child: const SizedBox(width: 200.0, height: 200.0),
               ),
             ),
           ),
@@ -222,7 +222,7 @@ void main() {
 
       // Drag to pan works because even though the viewport fits perfectly
       // around the child, there is no boundary.
-      final Offset childOffset = tester.getTopLeft(find.byType(Container));
+      final Offset childOffset = tester.getTopLeft(find.byType(SizedBox));
       final Offset childInterior = Offset(
         childOffset.dx + 20.0,
         childOffset.dy + 20.0,
@@ -268,7 +268,7 @@ void main() {
                 alignPanAxis: true,
                 boundaryMargin: const EdgeInsets.all(double.infinity),
                 transformationController: transformationController,
-                child: Container(width: 200.0, height: 200.0),
+                child: const SizedBox(width: 200.0, height: 200.0),
               ),
             ),
           ),
@@ -278,7 +278,7 @@ void main() {
       expect(transformationController.value, equals(Matrix4.identity()));
 
       // Perform a diagonal drag gesture.
-      final Offset childOffset = tester.getTopLeft(find.byType(Container));
+      final Offset childOffset = tester.getTopLeft(find.byType(SizedBox));
       final Offset childInterior = Offset(
         childOffset.dx + 20.0,
         childOffset.dy + 20.0,
@@ -308,7 +308,7 @@ void main() {
                 alignPanAxis: true,
                 boundaryMargin: const EdgeInsets.all(double.infinity),
                 transformationController: transformationController,
-                child: Container(width: 200.0, height: 200.0),
+                child: const SizedBox(width: 200.0, height: 200.0),
               ),
             ),
           ),
@@ -318,7 +318,7 @@ void main() {
       expect(transformationController.value, equals(Matrix4.identity()));
 
       // Perform a horizontally leaning diagonal drag gesture.
-      final Offset childOffset = tester.getTopLeft(find.byType(Container));
+      final Offset childOffset = tester.getTopLeft(find.byType(SizedBox));
       final Offset childInterior = Offset(
         childOffset.dx + 20.0,
         childOffset.dy + 10.0,
@@ -350,7 +350,7 @@ void main() {
                 boundaryMargin: const EdgeInsets.all(boundaryMargin),
                 minScale: minScale,
                 transformationController: transformationController,
-                child: Container(width: 200.0, height: 200.0),
+                child: const SizedBox(width: 200.0, height: 200.0),
               ),
             ),
           ),
@@ -358,7 +358,7 @@ void main() {
       );
 
       // Fling the child.
-      final Offset childOffset = tester.getTopLeft(find.byType(Container));
+      final Offset childOffset = tester.getTopLeft(find.byType(SizedBox));
       const Offset flingEnd = Offset(20.0, 15.0);
       await tester.flingFrom(childOffset, flingEnd, 1000.0);
       await tester.pump();
@@ -411,7 +411,7 @@ void main() {
                 boundaryMargin: const EdgeInsets.all(boundaryMargin),
                 minScale: minScale,
                 transformationController: transformationController,
-                child: Container(width: 200.0, height: 200.0),
+                child: const SizedBox(width: 200.0, height: 200.0),
               ),
             ),
           ),
@@ -423,7 +423,7 @@ void main() {
       expect(translation.y, 0.0);
 
       // Pan into the corner of the boundaries.
-      final Offset childOffset = tester.getTopLeft(find.byType(Container));
+      final Offset childOffset = tester.getTopLeft(find.byType(SizedBox));
       const Offset flingEnd = Offset(20.0, 15.0);
       await tester.flingFrom(childOffset, flingEnd, 1000.0);
       await tester.pumpAndSettle();
@@ -433,7 +433,7 @@ void main() {
 
       // Zoom out so the entire child is visible. The child will also be
       // translated in order to keep it inside the boundaries.
-      final Offset childCenter = tester.getCenter(find.byType(Container));
+      final Offset childCenter = tester.getCenter(find.byType(SizedBox));
       Offset scaleStart1 = Offset(childCenter.dx - 40.0, childCenter.dy);
       Offset scaleStart2 = Offset(childCenter.dx + 40.0, childCenter.dy);
       Offset scaleEnd1 = Offset(childCenter.dx - 10.0, childCenter.dy);
@@ -497,7 +497,7 @@ void main() {
                 boundaryMargin: const EdgeInsets.all(boundaryMargin),
                 minScale: minScale,
                 transformationController: transformationController,
-                child: Container(width: 200.0, height: 200.0),
+                child: const SizedBox(width: 200.0, height: 200.0),
               ),
             ),
           ),
@@ -510,12 +510,12 @@ void main() {
 
       // Pan into the corner of the boundaries in two gestures, since
       // alignPanAxis prevents diagonal panning.
-      final Offset childOffset1 = tester.getTopLeft(find.byType(Container));
+      final Offset childOffset1 = tester.getTopLeft(find.byType(SizedBox));
       const Offset flingEnd1 = Offset(20.0, 0.0);
       await tester.flingFrom(childOffset1, flingEnd1, 1000.0);
       await tester.pumpAndSettle();
       await tester.pump(const Duration(seconds: 5));
-      final Offset childOffset2 = tester.getTopLeft(find.byType(Container));
+      final Offset childOffset2 = tester.getTopLeft(find.byType(SizedBox));
       const Offset flingEnd2 = Offset(0.0, 15.0);
       await tester.flingFrom(childOffset2, flingEnd2, 1000.0);
       await tester.pumpAndSettle();
@@ -525,7 +525,7 @@ void main() {
 
       // Zoom out so the entire child is visible. The child will also be
       // translated in order to keep it inside the boundaries.
-      final Offset childCenter = tester.getCenter(find.byType(Container));
+      final Offset childCenter = tester.getCenter(find.byType(SizedBox));
       Offset scaleStart1 = Offset(childCenter.dx - 40.0, childCenter.dy);
       Offset scaleStart2 = Offset(childCenter.dx + 40.0, childCenter.dy);
       Offset scaleEnd1 = Offset(childCenter.dx - 10.0, childCenter.dy);
@@ -584,7 +584,7 @@ void main() {
             body: Center(
               child: InteractiveViewer(
                 transformationController: transformationController,
-                child: Container(width: 200.0, height: 200.0),
+                child: const SizedBox(width: 200.0, height: 200.0),
               ),
             ),
           ),
@@ -607,7 +607,7 @@ void main() {
               child: InteractiveViewer(
                 transformationController: transformationController,
                 scaleEnabled: false,
-                child: Container(width: 200.0, height: 200.0),
+                child: const SizedBox(width: 200.0, height: 200.0),
               ),
             ),
           ),
@@ -645,7 +645,7 @@ void main() {
                 onInteractionEnd: (ScaleEndDetails details){
                   currentVelocity = details.velocity;
                 },
-                child: Container(width: 200.0, height: 200.0),
+                child: const SizedBox(width: 200.0, height: 200.0),
               ),
             ),
           ),
@@ -684,7 +684,7 @@ void main() {
               maxScale: 100000,
               minScale: 0.01,
               transformationController: transformationController,
-              child: Container(width: 1000.0, height: 1000.0),
+              child: const SizedBox(width: 1000.0, height: 1000.0),
             ),
           )),
         ),
@@ -728,7 +728,7 @@ void main() {
                 onInteractionEnd: (ScaleEndDetails details){
                   currentVelocity = details.velocity;
                 },
-                child: Container(width: 200.0, height: 200.0),
+                child: const SizedBox(width: 200.0, height: 200.0),
               ),
             ),
           ),
@@ -818,7 +818,7 @@ void main() {
               child: InteractiveViewer(
                 boundaryMargin: const EdgeInsets.all(boundaryMargin),
                 transformationController: transformationController,
-                child: Container(width: 200.0, height: 200.0),
+                child: const SizedBox(width: 200.0, height: 200.0),
               ),
             ),
           ),
@@ -830,7 +830,7 @@ void main() {
       expect(translation.y, 0.0);
 
       // Start a pan gesture.
-      final Offset childCenter = tester.getCenter(find.byType(Container));
+      final Offset childCenter = tester.getCenter(find.byType(SizedBox));
       final TestGesture gesture = await tester.createGesture();
       await gesture.down(childCenter);
       await tester.pump();
@@ -922,7 +922,7 @@ void main() {
                     scale = details.scale;
                   },
                   transformationController: transformationController,
-                  child: Container(width: 200.0, height: 200.0),
+                  child: const SizedBox(width: 200.0, height: 200.0),
                 ),
               ),
             ),
@@ -936,7 +936,7 @@ void main() {
 
       // Pinch to zoom isn't immediately detected for a small amount of
       // movement due to the GestureDetector.
-      final Offset childOffset = tester.getTopLeft(find.byType(Container));
+      final Offset childOffset = tester.getTopLeft(find.byType(SizedBox));
       final Offset childInterior = Offset(
         childOffset.dx + 20.0,
         childOffset.dy + 20.0,

packages/flutter/test/widgets/keep_alive_test.dart

@@ -103,7 +103,7 @@ void main() {
           addAutomaticKeepAlives: false,
           addRepaintBoundaries: false,
           addSemanticIndexes: false,
-          children: generateList(Container(height: 12.3, child: const Placeholder())), // about 50 widgets visible
+          children: generateList(const SizedBox(height: 12.3, child: Placeholder())), // about 50 widgets visible
         ),
       ),
     );

packages/flutter/test/widgets/list_view_builder_test.dart

@@ -22,7 +22,7 @@ void main() {
             itemExtent: 100.0,
             itemBuilder: (BuildContext context, int index) {
               callbackTracker.add(index);
-              return Container(
+              return SizedBox(
                 key: ValueKey<int>(index),
                 height: 100.0,
                 child: Text('$index'),
@@ -70,7 +70,7 @@ void main() {
 
     final IndexedWidgetBuilder itemBuilder = (BuildContext context, int index) {
       callbackTracker.add(index);
-      return Container(
+      return SizedBox(
         key: ValueKey<int>(index),
         width: 500.0, // this should be ignored
         height: 400.0, // should be overridden by itemExtent
@@ -143,7 +143,7 @@ void main() {
 
     final IndexedWidgetBuilder itemBuilder = (BuildContext context, int index) {
       callbackTracker.add(index);
-      return Container(
+      return SizedBox(
         key: ValueKey<int>(index),
         width: 400.0, // this should be overridden by itemExtent
         height: 500.0, // this should be ignored

packages/flutter/test/widgets/list_view_correction_test.dart

@@ -14,13 +14,13 @@ void main() {
         child: ListView(
           cacheExtent: 0.0,
           controller: controller,
-          children: <Widget>[
-            Container(height: 400.0, child: const Text('1')),
-            Container(height: 400.0, child: const Text('2')),
-            Container(height: 400.0, child: const Text('3')),
-            Container(height: 400.0, child: const Text('4')),
-            Container(height: 400.0, child: const Text('5')),
-            Container(height: 400.0, child: const Text('6')),
+          children: const <Widget>[
+            SizedBox(height: 400.0, child: Text('1')),
+            SizedBox(height: 400.0, child: Text('2')),
+            SizedBox(height: 400.0, child: Text('3')),
+            SizedBox(height: 400.0, child: Text('4')),
+            SizedBox(height: 400.0, child: Text('5')),
+            SizedBox(height: 400.0, child: Text('6')),
           ],
         ),
       ),
@@ -37,13 +37,13 @@ void main() {
         child: ListView(
           cacheExtent: 0.0,
           controller: controller,
-          children: <Widget>[
-            Container(height: 200.0, child: const Text('1')),
-            Container(height: 400.0, child: const Text('2')),
-            Container(height: 400.0, child: const Text('3')),
-            Container(height: 400.0, child: const Text('4')),
-            Container(height: 400.0, child: const Text('5')),
-            Container(height: 400.0, child: const Text('6')),
+          children: const <Widget>[
+            SizedBox(height: 200.0, child: Text('1')),
+            SizedBox(height: 400.0, child: Text('2')),
+            SizedBox(height: 400.0, child: Text('3')),
+            SizedBox(height: 400.0, child: Text('4')),
+            SizedBox(height: 400.0, child: Text('5')),
+            SizedBox(height: 400.0, child: Text('6')),
           ],
         ),
       ),
@@ -72,13 +72,13 @@ void main() {
         textDirection: TextDirection.ltr,
         child: ListView(
           controller: controller,
-          children: <Widget>[
-            Container(height: 400.0, child: const Text('1')),
-            Container(height: 400.0, child: const Text('2')),
-            Container(height: 400.0, child: const Text('3')),
-            Container(height: 400.0, child: const Text('4')),
-            Container(height: 400.0, child: const Text('5')),
-            Container(height: 400.0, child: const Text('6')),
+          children: const <Widget>[
+            SizedBox(height: 400.0, child: Text('1')),
+            SizedBox(height: 400.0, child: Text('2')),
+            SizedBox(height: 400.0, child: Text('3')),
+            SizedBox(height: 400.0, child: Text('4')),
+            SizedBox(height: 400.0, child: Text('5')),
+            SizedBox(height: 400.0, child: Text('6')),
           ],
         ),
       ),
@@ -94,13 +94,13 @@ void main() {
         textDirection: TextDirection.ltr,
         child: ListView(
           controller: controller,
-          children: <Widget>[
-            Container(height: 200.0, child: const Text('1')),
-            Container(height: 400.0, child: const Text('2')),
-            Container(height: 400.0, child: const Text('3')),
-            Container(height: 400.0, child: const Text('4')),
-            Container(height: 400.0, child: const Text('5')),
-            Container(height: 400.0, child: const Text('6')),
+          children: const <Widget>[
+            SizedBox(height: 200.0, child: Text('1')),
+            SizedBox(height: 400.0, child: Text('2')),
+            SizedBox(height: 400.0, child: Text('3')),
+            SizedBox(height: 400.0, child: Text('4')),
+            SizedBox(height: 400.0, child: Text('5')),
+            SizedBox(height: 400.0, child: Text('6')),
           ],
         ),
       ),
@@ -129,11 +129,11 @@ void main() {
         textDirection: TextDirection.ltr,
         child: ListView(
           controller: controller,
-          children: <Widget>[
-            Container(height: 400.0, child: const Text('0')),
-            Container(height: 400.0, child: const Text('1')),
-            Container(height: 400.0, child: const Text('2')),
-            Container(height: 400.0, child: const Text('3')),
+          children: const <Widget>[
+            SizedBox(height: 400.0, child: Text('0')),
+            SizedBox(height: 400.0, child: Text('1')),
+            SizedBox(height: 400.0, child: Text('2')),
+            SizedBox(height: 400.0, child: Text('3')),
           ],
         ),
       ),
@@ -143,20 +143,20 @@ void main() {
     expect(find.text('2'), findsNothing);
     expect(find.text('3'), findsNothing);
 
-    final Finder findItemA = find.descendant(of: find.byType(Container), matching: find.text('A'));
-    final Finder findItemB = find.descendant(of: find.byType(Container), matching: find.text('B'));
+    final Finder findItemA = find.descendant(of: find.byType(SizedBox), matching: find.text('A'));
+    final Finder findItemB = find.descendant(of: find.byType(SizedBox), matching: find.text('B'));
     await tester.pumpWidget(
       Directionality(
         textDirection: TextDirection.ltr,
         child: ListView(
           controller: controller,
-          children: <Widget>[
-            Container(height: 10.0, child: const Text('A')),
-            Container(height: 10.0, child: const Text('B')),
-            Container(height: 400.0, child: const Text('0')),
-            Container(height: 400.0, child: const Text('1')),
-            Container(height: 400.0, child: const Text('2')),
-            Container(height: 400.0, child: const Text('3')),
+          children: const <Widget>[
+            SizedBox(height: 10.0, child: Text('A')),
+            SizedBox(height: 10.0, child: Text('B')),
+            SizedBox(height: 400.0, child: Text('0')),
+            SizedBox(height: 400.0, child: Text('1')),
+            SizedBox(height: 400.0, child: Text('2')),
+            SizedBox(height: 400.0, child: Text('3')),
           ],
         ),
       ),
@@ -179,13 +179,13 @@ void main() {
         textDirection: TextDirection.ltr,
         child: ListView(
           controller: controller,
-          children: <Widget>[
-            Container(height: 200.0, child: const Text('A')),
-            Container(height: 200.0, child: const Text('B')),
-            Container(height: 400.0, child: const Text('0')),
-            Container(height: 400.0, child: const Text('1')),
-            Container(height: 400.0, child: const Text('2')),
-            Container(height: 400.0, child: const Text('3')),
+          children: const <Widget>[
+            SizedBox(height: 200.0, child: Text('A')),
+            SizedBox(height: 200.0, child: Text('B')),
+            SizedBox(height: 400.0, child: Text('0')),
+            SizedBox(height: 400.0, child: Text('1')),
+            SizedBox(height: 400.0, child: Text('2')),
+            SizedBox(height: 400.0, child: Text('3')),
           ],
         ),
       ),

packages/flutter/test/widgets/list_view_horizontal_test.dart

@@ -11,7 +11,7 @@ Widget buildFrame({ bool reverse = false, required TextDirection textDirection }
   return Directionality(
     textDirection: textDirection,
     child: Center(
-      child: Container(
+      child: SizedBox(
         height: 50.0,
         child: ListView(
           itemExtent: 290.0,
@@ -19,9 +19,7 @@ Widget buildFrame({ bool reverse = false, required TextDirection textDirection }
           reverse: reverse,
           physics: const BouncingScrollPhysics(),
           children: items.map<Widget>((int item) {
-            return Container(
-              child: Text('$item'),
-            );
+            return Text('$item');
           }).toList(),
         ),
       ),

packages/flutter/test/widgets/list_view_misc_test.dart

@@ -14,10 +14,10 @@ void main() {
         textDirection: TextDirection.ltr,
         child: ListView(
           key: blockKey,
-          children: <Widget>[
-            Container(
+          children: const <Widget>[
+            SizedBox(
               height: 200.0, // less than 600, the height of the test area
-              child: const Text('Hello'),
+              child: Text('Hello'),
             ),
           ],
         ),
@@ -42,10 +42,10 @@ void main() {
         textDirection: TextDirection.ltr,
         child: ListView(
           key: blockKey,
-          children: <Widget>[
-            Container(
+          children: const <Widget>[
+            SizedBox(
               height: 2000.0, // more than 600, the height of the test area
-              child: const Text('Hello'),
+              child: Text('Hello'),
             ),
           ],
         ),

packages/flutter/test/widgets/list_view_test.dart

@@ -402,7 +402,7 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 200.0,
             child: ListView(
               cacheExtent: 500.0,
@@ -431,12 +431,12 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 200.0,
             child: ListView(
               cacheExtent: 500.0,
-              children: <Widget>[
-                Container(
+              children: const <Widget>[
+                SizedBox(
                   height: 100.0,
                 ),
               ],
@@ -456,19 +456,19 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 200.0,
             child: ListView(
               itemExtent: 100.0,
               cacheExtent: 500.0,
-              children: <Widget>[
-                Container(
+              children: const <Widget>[
+                SizedBox(
                   height: 100.0,
                 ),
-                Container(
+                SizedBox(
                   height: 100.0,
                 ),
-                Container(
+                SizedBox(
                   height: 100.0,
                 ),
               ],
@@ -486,13 +486,13 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 200.0,
             child: ListView(
               itemExtent: 100.0,
               cacheExtent: 500.0,
-              children: <Widget>[
-                Container(
+              children: const <Widget>[
+                SizedBox(
                   height: 100.0,
                 ),
               ],
@@ -511,13 +511,13 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 200.0,
             child: ListView(
               scrollDirection: Axis.horizontal,
               itemExtent: 100.0,
-              children: <Widget>[
-                Container(
+              children: const <Widget>[
+                SizedBox(
                   height: 100.0,
                 ),
               ],
@@ -547,15 +547,15 @@ void main() {
       return Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 200.0,
             width: 100.0,
             child: ListView(
               controller: controller,
               scrollDirection: scrollDirection,
               itemExtent: 50.0,
-              children: <Widget>[
-                Container(
+              children: const <Widget>[
+                SizedBox(
                   height: 50.0,
                   width: 50.0,
                 ),

packages/flutter/test/widgets/list_view_viewporting_test.dart

@@ -24,7 +24,7 @@ void main() {
           left: ListView.builder(
             itemBuilder: (BuildContext context, int index) {
               callbackTracker.add(index);
-              return Container(
+              return SizedBox(
                 key: ValueKey<int>(index),
                 height: 100.0,
                 child: Text('$index'),
@@ -70,7 +70,7 @@ void main() {
 
     final IndexedWidgetBuilder itemBuilder = (BuildContext context, int index) {
       callbackTracker.add(index);
-      return Container(
+      return SizedBox(
         key: ValueKey<int>(index),
         width: 500.0, // this should be ignored
         height: 200.0,
@@ -133,7 +133,7 @@ void main() {
 
     final IndexedWidgetBuilder itemBuilder = (BuildContext context, int index) {
       callbackTracker.add(index);
-      return Container(
+      return SizedBox(
         key: ValueKey<int>(index),
         height: 500.0, // this should be ignored
         width: 200.0,
@@ -184,7 +184,7 @@ void main() {
 
     final IndexedWidgetBuilder itemBuilder = (BuildContext context, int index) {
       callbackTracker.add(index);
-      return Container(
+      return SizedBox(
         key: ValueKey<int>(index),
         width: 500.0, // this should be ignored
         height: 220.0,
@@ -440,18 +440,18 @@ void main() {
         Directionality(
             textDirection: TextDirection.ltr,
             child: Center(
-              child: Container(
+              child: SizedBox(
                   height: 200.0,
                   child: ListView(
                     cacheExtent: 500.0,
                     controller: ScrollController(initialScrollOffset: 300.0),
-                    children: <Widget>[
-                      Container(height: 140.0, child: text),
-                      Container(height: 160.0, child: text),
-                      Container(height: 90.0, child: text),
-                      Container(height: 110.0, child: text),
-                      Container(height: 80.0, child: text),
-                      Container(height: 70.0, child: text),
+                    children: const <Widget>[
+                      SizedBox(height: 140.0, child: text),
+                      SizedBox(height: 160.0, child: text),
+                      SizedBox(height: 90.0, child: text),
+                      SizedBox(height: 110.0, child: text),
+                      SizedBox(height: 80.0, child: text),
+                      SizedBox(height: 70.0, child: text),
                     ],
                   ),
               ),
@@ -467,7 +467,7 @@ void main() {
     await tester.pumpWidget(
         MaterialApp(
             home: Scaffold(
-                body: Container(
+                body: SizedBox(
                     height: 500.0,
                     child: CustomScrollView(
                       controller: ScrollController(initialScrollOffset: 120.0),
@@ -479,9 +479,9 @@ void main() {
                             delegate: ListView.builder(
                                 itemExtent: 100.0,
                                 itemCount: 100,
-                                itemBuilder: (_, __) => Container(
+                                itemBuilder: (_, __) => const SizedBox(
                                   height: 40.0,
-                                  child: const Text('hey'),
+                                  child: Text('hey'),
                                 )).childrenDelegate),
                       ],
                     ),
@@ -498,7 +498,7 @@ void main() {
     await tester.pumpWidget(
         Directionality(
           textDirection: TextDirection.rtl,
-          child: Container(
+          child: SizedBox(
             height: 200.0,
             child: ListView.builder(
               padding: EdgeInsets.zero,

packages/flutter/test/widgets/list_view_with_inherited_test.dart

@@ -20,7 +20,7 @@ Widget buildCard(BuildContext context, int index) {
     return const SizedBox(height: 100);
   }
 
-  return Container(
+  return SizedBox(
     key: ValueKey<String>(items[index]),
     height: 100.0,
     child: DefaultTextStyle(

packages/flutter/test/widgets/list_wheel_scroll_view_test.dart

@@ -151,7 +151,7 @@ void main() {
             onSelectedItemChanged: (_) { },
             childDelegate: ListWheelChildLoopingListDelegate(
               children: List<Widget>.generate(10, (int index) {
-                return Container(
+                return SizedBox(
                   width: 400.0,
                   height: 100.0,
                   child: Text(index.toString()),
@@ -164,13 +164,13 @@ void main() {
 
       // The first item is at the center of the viewport.
       expect(
-      tester.getTopLeft(find.widgetWithText(Container, '0')),
+      tester.getTopLeft(find.widgetWithText(SizedBox, '0')),
       const Offset(0.0, 250.0),
       );
 
       // The last item is just before the first item.
       expect(
-        tester.getTopLeft(find.widgetWithText(Container, '9')),
+        tester.getTopLeft(find.widgetWithText(SizedBox, '9')),
         const Offset(0.0, 150.0),
       );
 
@@ -179,7 +179,7 @@ void main() {
 
       // We have passed the end of the list, the list should have looped back.
       expect(
-        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        tester.getTopLeft(find.widgetWithText(SizedBox, '0')),
         const Offset(0.0, 250.0),
       );
     });
@@ -197,7 +197,7 @@ void main() {
             onSelectedItemChanged: (_) { },
             childDelegate: ListWheelChildBuilderDelegate(
               builder: (BuildContext context, int index) {
-                return Container(
+                return SizedBox(
                   width: 400.0,
                   height: 100.0,
                   child: Text(index.toString()),
@@ -212,7 +212,7 @@ void main() {
       controller.jumpTo(-100000.0);
       await tester.pump();
       expect(
-        tester.getTopLeft(find.widgetWithText(Container, '-1000')),
+        tester.getTopLeft(find.widgetWithText(SizedBox, '-1000')),
         const Offset(0.0, 250.0),
       );
 
@@ -220,7 +220,7 @@ void main() {
       controller.jumpTo(100000.0);
       await tester.pump();
       expect(
-        tester.getTopLeft(find.widgetWithText(Container, '1000')),
+        tester.getTopLeft(find.widgetWithText(SizedBox, '1000')),
         const Offset(0.0, 250.0),
       );
     });
@@ -242,7 +242,7 @@ void main() {
               builder: (BuildContext context, int index) {
                 if (index < -15 || index > -5)
                   return null;
-                return Container(
+                return SizedBox(
                   width: 400.0,
                   height: 100.0,
                   child: CustomPaint(
@@ -362,7 +362,7 @@ void main() {
                 expect(builtChildren.contains(index), false);
                 builtChildren.add(index);
 
-                return Container(
+                return SizedBox(
                   width: 400.0,
                   height: 100.0,
                   child: Text(index.toString()),
@@ -616,10 +616,10 @@ void main() {
           textDirection: TextDirection.ltr,
           child: ListWheelScrollView(
             itemExtent: 100.0,
-            children: <Widget>[
-              Container(
+            children: const <Widget>[
+              SizedBox(
                 width: 200.0,
-                child: const Center(
+                child: Center(
                   child: Text('blah'),
                 ),
               ),
@@ -673,10 +673,10 @@ void main() {
           child: ListWheelScrollView(
             controller: controller,
             itemExtent: 100.0,
-            children: <Widget>[
-              Container(
+            children: const <Widget>[
+              SizedBox(
                 width: 200.0,
-                child: const Center(
+                child: Center(
                   child: Text('blah'),
                 ),
               ),
@@ -703,10 +703,10 @@ void main() {
             controller: controller,
             diameterRatio: 3.0,
             itemExtent: 100.0,
-            children: <Widget>[
-              Container(
+            children: const <Widget>[
+              SizedBox(
                 width: 200.0,
-                child: const Center(
+                child: Center(
                   child: Text('blah'),
                 ),
               ),
@@ -732,10 +732,10 @@ void main() {
             controller: controller,
             perspective: 0.0001,
             itemExtent: 100.0,
-            children: <Widget>[
-              Container(
+            children: const <Widget>[
+              SizedBox(
                 width: 200.0,
-                child: const Center(
+                child: Center(
                   child: Text('blah'),
                 ),
               ),
@@ -761,10 +761,10 @@ void main() {
           child: ListWheelScrollView(
             controller: controller,
             itemExtent: 100.0,
-            children: <Widget>[
-              Container(
+            children: const <Widget>[
+              SizedBox(
                 width: 200.0,
-                child: const Center(
+                child: Center(
                   child: Text('blah'),
                 ),
               ),
@@ -794,10 +794,10 @@ void main() {
             controller: controller,
             itemExtent: 100.0,
             offAxisFraction: 0.5,
-            children: <Widget>[
-              Container(
+            children: const <Widget>[
+              SizedBox(
                 width: 200.0,
-                child: const Center(
+                child: Center(
                   child: Text('blah'),
                 ),
               ),
@@ -840,10 +840,10 @@ void main() {
             offAxisFraction: 0.5,
             useMagnifier: true,
             magnification: 1.5,
-            children: <Widget>[
-              Container(
+            children: const <Widget>[
+              SizedBox(
                 width: 200.0,
-                child: const Center(
+                child: Center(
                   child: Text('blah'),
                 ),
               ),
@@ -888,10 +888,10 @@ void main() {
           child: ListWheelScrollView(
             itemExtent: 100.0,
             onSelectedItemChanged: onItemChange,
-            children: <Widget>[
-              Container(
+            children: const <Widget>[
+              SizedBox(
                 width: 200.0,
-                child: const Center(
+                child: Center(
                   child: Text('blah'),
                 ),
               ),
@@ -1275,7 +1275,7 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 500.0,
             width: 300.0,
             child: ListWheelScrollView(
@@ -1284,7 +1284,7 @@ void main() {
               children: outerChildren = List<Widget>.generate(10, (int i) {
                 return Container(
                   child: Center(
-                    child: innerChildren[i] = Container(
+                    child: innerChildren[i] = SizedBox(
                       height: 50.0,
                       width: 50.0,
                       child: Text('Item $i'),
@@ -1346,7 +1346,7 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 500.0,
             width: 300.0,
             child: ListWheelScrollView(
@@ -1356,7 +1356,7 @@ void main() {
               outerChildren = List<Widget>.generate(10, (int i) {
                 return Container(
                   child: Center(
-                    child: innerChildren[i] = Container(
+                    child: innerChildren[i] = SizedBox(
                       height: 50.0,
                       width: 50.0,
                       child: Text('Item $i'),

packages/flutter/test/widgets/mouse_region_test.dart

@@ -575,10 +575,10 @@ void main() {
   });
 
   testWidgets('applies mouse cursor', (WidgetTester tester) async {
-    await tester.pumpWidget(_Scaffold(
+    await tester.pumpWidget(const _Scaffold(
       topLeft: MouseRegion(
         cursor: SystemMouseCursors.text,
-        child: Container(width: 10, height: 10),
+        child: SizedBox(width: 10, height: 10),
       ),
     ));
 
@@ -1085,7 +1085,7 @@ void main() {
               height: 100,
               width: 10,
               alignment: moved ? Alignment.topLeft : Alignment.bottomLeft,
-              child: Container(
+              child: SizedBox(
                 height: 10,
                 width: 10,
                 child: HoverClient(
@@ -1363,7 +1363,7 @@ void main() {
     addTearDown(gesture.removePointer);
 
     await tester.pumpWidget(_Scaffold(
-      topLeft: Container(
+      topLeft: SizedBox(
         height: 10,
         width: 10,
         child: MouseRegion(
@@ -1384,7 +1384,7 @@ void main() {
     logs.clear();
 
     await tester.pumpWidget(_Scaffold(
-      topLeft: Container(
+      topLeft: SizedBox(
         height: 10,
         width: 10,
         child: MouseRegion(
@@ -1405,7 +1405,7 @@ void main() {
 
     // Compare: It repaints if the MouseRegion is deactivated.
     await tester.pumpWidget(_Scaffold(
-      topLeft: Container(
+      topLeft: SizedBox(
         height: 10,
         width: 10,
         child: MouseRegion(
@@ -1430,7 +1430,7 @@ void main() {
     final VoidCallback onPaintChild = () { logs.add('paint'); };
 
     await tester.pumpWidget(_Scaffold(
-      topLeft: Container(
+      topLeft: SizedBox(
         height: 10,
         width: 10,
         child: MouseRegion(
@@ -1450,7 +1450,7 @@ void main() {
     logs.clear();
 
     await tester.pumpWidget(_Scaffold(
-      topLeft: Container(
+      topLeft: SizedBox(
         height: 10,
         width: 10,
         child: MouseRegion(
@@ -1476,7 +1476,7 @@ void main() {
     final VoidCallback onPaintChild = () { logPaints.add('paint'); };
 
     await tester.pumpWidget(_Scaffold(
-      topLeft: Container(
+      topLeft: SizedBox(
         height: 10,
         width: 10,
         child: MouseRegion(
@@ -1496,7 +1496,7 @@ void main() {
     logEnters.clear();
 
     await tester.pumpWidget(_Scaffold(
-      topLeft: Container(
+      topLeft: SizedBox(
         height: 10,
         width: 10,
         child: MouseRegion(
@@ -1526,7 +1526,7 @@ void main() {
     final VoidCallback onPaintChild = () { logPaints.add('paint'); };
 
     await tester.pumpWidget(_Scaffold(
-      topLeft: Container(
+      topLeft: SizedBox(
         height: 10,
         width: 10,
         child: MouseRegion(
@@ -1548,7 +1548,7 @@ void main() {
     logEnters.clear();
 
     await tester.pumpWidget(_Scaffold(
-      topLeft: Container(
+      topLeft: SizedBox(
         height: 10,
         width: 10,
         child: MouseRegion(
@@ -1569,7 +1569,7 @@ void main() {
     logEnters.clear();
 
     await tester.pumpWidget(_Scaffold(
-      topLeft: Container(
+      topLeft: SizedBox(
         height: 10,
         width: 10,
         child: MouseRegion(

packages/flutter/test/widgets/nested_scroll_view_test.dart

@@ -71,43 +71,41 @@ Widget buildTest({
               body: TabBarView(
                 children: <Widget>[
                   ListView(
-                    children: <Widget>[
-                      Container(
+                    children: const <Widget>[
+                      SizedBox(
                         height: 300.0,
-                        child: const Text('aaa1'),
+                        child: Text('aaa1'),
                       ),
-                      Container(
+                      SizedBox(
                         height: 200.0,
-                        child: const Text('aaa2'),
+                        child: Text('aaa2'),
                       ),
-                      Container(
+                      SizedBox(
                         height: 100.0,
-                        child: const Text('aaa3'),
+                        child: Text('aaa3'),
                       ),
-                      Container(
+                      SizedBox(
                         height: 50.0,
-                        child: const Text('aaa4'),
+                        child: Text('aaa4'),
                       ),
                     ],
                   ),
                   ListView(
                     dragStartBehavior: DragStartBehavior.down,
-                    children: <Widget>[
-                      Container(
+                    children: const <Widget>[
+                      SizedBox(
                         height: 100.0,
-                        child: const Text('bbb1'),
+                        child: Text('bbb1'),
                       ),
                     ],
                   ),
-                  Container(
-                    child: const Center(child: Text('ccc1')),
-                  ),
+                  const Center(child: Text('ccc1')),
                   ListView(
                     dragStartBehavior: DragStartBehavior.down,
-                    children: <Widget>[
-                      Container(
+                    children: const <Widget>[
+                      SizedBox(
                         height: 10000.0,
-                        child: const Text('ddd1'),
+                        child: Text('ddd1'),
                       ),
                     ],
                   ),
@@ -773,11 +771,11 @@ void main() {
                   ),
                 ];
               },
-              body: SingleChildScrollView(
+              body: const SingleChildScrollView(
                 dragStartBehavior: DragStartBehavior.down,
-                child: Container(
+                child: SizedBox(
                   height: 1000.0,
-                  child: const Placeholder(key: key2),
+                  child: Placeholder(key: key2),
                 ),
               ),
             ),
@@ -2391,9 +2389,9 @@ class _TestLayoutExtentIsNegative extends StatelessWidget {
                   pinned: true,
                   forceElevated: innerBoxIsScrolled,
                   backgroundColor: Colors.blue[300],
-                  title: Container(
+                  title: const SizedBox(
                     height: 50,
-                    child: const Center(
+                    child: Center(
                       child: Text('Sticky Header'),
                     ),
                   ),

packages/flutter/test/widgets/overflow_box_test.dart

@@ -58,7 +58,7 @@ void main() {
         child: SizedOverflowBox(
           size: const Size(100.0, 100.0),
           alignment: Alignment.topRight,
-          child: Container(height: 50.0, width: 50.0, key: inner),
+          child: SizedBox(height: 50.0, width: 50.0, key: inner),
         ),
       ),
     ));
@@ -81,7 +81,7 @@ void main() {
         child: SizedOverflowBox(
           size: const Size(100.0, 100.0),
           alignment: AlignmentDirectional.bottomStart,
-          child: Container(height: 50.0, width: 50.0, key: inner),
+          child: SizedBox(height: 50.0, width: 50.0, key: inner),
         ),
       ),
     ));

packages/flutter/test/widgets/overscroll_indicator_test.dart

@@ -65,11 +65,11 @@ void main() {
           axisDirection: AxisDirection.down,
           color: const Color(0x0DFFFFFF),
           notificationPredicate: (ScrollNotification notification) => notification.depth == 1,
-          child: SingleChildScrollView(
+          child: const SingleChildScrollView(
             scrollDirection: Axis.horizontal,
-            child: Container(
+            child: SizedBox(
                 width: 600.0,
-                child: const CustomScrollView(
+                child: CustomScrollView(
                   slivers: <Widget>[
                     SliverToBoxAdapter(child: SizedBox(height: 2000.0)),
                   ],

packages/flutter/test/widgets/pageable_list_test.dart

@@ -11,7 +11,7 @@ final List<GlobalKey> globalKeys = defaultPages.map<GlobalKey>((_) => GlobalKey(
 int? currentPage;
 
 Widget buildPage(int page) {
-  return Container(
+  return SizedBox(
     key: globalKeys[page],
     width: pageSize.width,
     height: pageSize.height,
@@ -36,7 +36,7 @@ Widget buildFrame({
   return Directionality(
     textDirection: textDirection,
     child: Center(
-      child: Container(
+      child: SizedBox(
         width: pageSize.width, height: pageSize.height, child: child,
       ),
     ),

packages/flutter/test/widgets/physical_model_test.dart

@@ -141,11 +141,11 @@ void main() {
     //            │
     // ────────────────────────────
     testWidgets('entirely overlapping, direct child', (WidgetTester tester) async {
-      final List<Widget> children = <Widget>[
-        Container(
+      const List<Widget> children = <Widget>[
+        SizedBox(
           width: 300,
           height: 300,
-          child: const Material(
+          child: Material(
             elevation: 1.0,
             color: Colors.green,
             child: Material(
@@ -169,19 +169,19 @@ void main() {
     //         │          │
     // ────────────────────────────
     testWidgets('entirely overlapping, correct painting order', (WidgetTester tester) async {
-      final List<Widget> children = <Widget>[
-        Container(
+      const List<Widget> children = <Widget>[
+        SizedBox(
           width: 300,
           height: 300,
-          child: const Material(
+          child: Material(
             elevation: 1.0,
             color: Colors.green,
           ),
         ),
-        Container(
+        SizedBox(
           width: 300,
           height: 300,
-          child: const Material(
+          child: Material(
             elevation: 2.0,
             color: Colors.blue,
           ),
@@ -201,19 +201,19 @@ void main() {
     //         │        │
     // ────────────────────────────
     testWidgets('entirely overlapping, wrong painting order', (WidgetTester tester) async {
-      final List<Widget> children = <Widget>[
-        Container(
+      const List<Widget> children = <Widget>[
+        SizedBox(
           width: 300,
           height: 300,
-          child: const Material(
+          child: Material(
             elevation: 2.0,
             color: Colors.green,
           ),
         ),
-        Container(
+        SizedBox(
           width: 300,
           height: 300,
-          child: const Material(
+          child: Material(
             elevation: 1.0,
             color: Colors.blue,
           ),
@@ -237,10 +237,10 @@ void main() {
       final List<Widget> children = <Widget>[
         Positioned.fromRect(
           rect: const Rect.fromLTWH(150, 150, 150, 150),
-          child: Container(
+          child: const SizedBox(
             width: 300,
             height: 300,
-            child: const Material(
+            child: Material(
               elevation: 3.0,
               color: Colors.brown,
             ),
@@ -248,10 +248,10 @@ void main() {
         ),
         Positioned.fromRect(
           rect: const Rect.fromLTWH(20, 20, 140, 150),
-          child: Container(
+          child: const SizedBox(
             width: 300,
             height: 300,
-            child: const Material(
+            child: Material(
               elevation: 2.0,
               color: Colors.red,
               shape: CircleBorder(),
@@ -275,10 +275,10 @@ void main() {
       final List<Widget> children = <Widget>[
         Positioned.fromRect(
           rect: const Rect.fromLTWH(20, 20, 140, 150),
-          child: Container(
+          child: const SizedBox(
             width: 300,
             height: 300,
-            child: const Material(
+            child: Material(
               elevation: 3.0,
               color: Colors.brown,
             ),
@@ -286,10 +286,10 @@ void main() {
         ),
         Positioned.fromRect(
           rect: const Rect.fromLTWH(50, 50, 100, 100),
-          child: Container(
+          child: const SizedBox(
             width: 300,
             height: 300,
-            child: const Material(
+            child: Material(
               elevation: 2.0,
               color: Colors.red,
               shape: CircleBorder(),
@@ -313,10 +313,10 @@ void main() {
       final List<Widget> children = <Widget>[
         Positioned.fromRect(
           rect: const Rect.fromLTWH(150, 150, 150, 150),
-          child: Container(
+          child: const SizedBox(
             width: 300,
             height: 300,
-            child: const Material(
+            child: Material(
               elevation: 3.0,
               color: Colors.brown,
             ),
@@ -324,10 +324,10 @@ void main() {
         ),
         Positioned.fromRect(
           rect: const Rect.fromLTWH(30, 20, 150, 150),
-          child: Container(
+          child: const SizedBox(
             width: 300,
             height: 300,
-            child: const Material(
+            child: Material(
               elevation: 2.0,
               color: Colors.red,
               shape: CircleBorder(),
@@ -354,10 +354,10 @@ void main() {
       final List<Widget> children = <Widget>[
         Positioned.fromRect(
           rect: const Rect.fromLTWH(150, 150, 150, 150),
-          child: Container(
+          child: const SizedBox(
             width: 300,
             height: 300,
-            child: const Material(
+            child: Material(
               elevation: 1.0,
               color: Colors.brown,
               child: Padding(
@@ -372,10 +372,10 @@ void main() {
         ),
         Positioned.fromRect(
           rect: const Rect.fromLTWH(30, 20, 180, 180),
-          child: Container(
+          child: const SizedBox(
             width: 300,
             height: 300,
-            child: const Material(
+            child: Material(
               elevation: 1.0,
               color: Colors.red,
             ),
@@ -398,10 +398,10 @@ void main() {
       final List<Widget> children = <Widget>[
         Positioned.fromRect(
           rect: const Rect.fromLTWH(150, 150, 150, 150),
-          child: Container(
+          child: const SizedBox(
             width: 300,
             height: 300,
-            child: const Material(
+            child: Material(
               elevation: 3.0,
               color: Colors.brown,
             ),
@@ -409,10 +409,10 @@ void main() {
         ),
         Positioned.fromRect(
           rect: const Rect.fromLTWH(30, 20, 150, 150),
-          child: Container(
+          child: const SizedBox(
             width: 300,
             height: 300,
-            child: const Material(
+            child: Material(
               elevation: 2.0,
               color: Colors.red,
               shape: CircleBorder(),
@@ -442,7 +442,7 @@ void main() {
       final List<Widget> children = <Widget>[
         Positioned.fromRect(
           rect: const Rect.fromLTWH(140, 100, 140, 150),
-          child: Container(
+          child: SizedBox(
             width: 300,
             height: 300,
             child: Transform.rotate(
@@ -456,10 +456,10 @@ void main() {
         ),
         Positioned.fromRect(
           rect: const Rect.fromLTWH(50, 50, 100, 100),
-          child: Container(
+          child: const SizedBox(
             width: 300,
             height: 300,
-            child: const Material(
+            child: Material(
                 elevation: 2.0,
                 color: Colors.red,
                 shape: CircleBorder()),
@@ -483,7 +483,7 @@ void main() {
       final List<Widget> children = <Widget>[
         Positioned.fromRect(
           rect: const Rect.fromLTWH(140, 100, 140, 150),
-          child: Container(
+          child: SizedBox(
             width: 300,
             height: 300,
             child: Transform.rotate(
@@ -497,10 +497,10 @@ void main() {
         ),
         Positioned.fromRect(
           rect: const Rect.fromLTWH(50, 50, 100, 100),
-          child: Container(
+          child: const SizedBox(
             width: 300,
             height: 300,
-            child: const Material(
+            child: Material(
                 elevation: 2.0,
                 color: Colors.red,
                 shape: CircleBorder()),

packages/flutter/test/widgets/platform_view_test.dart

@@ -1885,16 +1885,16 @@ void main() {
       viewsController.registerViewType('webview');
 
       await tester.pumpWidget(
-        Container(width: 300, height: 600,
+        SizedBox(width: 300, height: 600,
           child: Stack(
             alignment: Alignment.topLeft,
             children: <Widget>[
               Transform.translate(
                 offset: const Offset(0, 100),
-                child: Container(
+                child: const SizedBox(
                   width: 300,
                   height: 500,
-                  child: const UiKitView(viewType: 'webview', layoutDirection: TextDirection.ltr)),),
+                  child: UiKitView(viewType: 'webview', layoutDirection: TextDirection.ltr)),),
               Transform.translate(
                 offset: const Offset(0, 500),
                 child: Container(

packages/flutter/test/widgets/positioned_test.dart

@@ -86,7 +86,7 @@ void main() {
       Directionality(
         textDirection: TextDirection.ltr,
         child: Center(
-          child: Container(
+          child: SizedBox(
             height: 100.0,
             width: 100.0,
             child: Stack(

packages/flutter/test/widgets/reorderable_list_test.dart

@@ -25,7 +25,7 @@ void main() {
                     });
                   },
                   itemBuilder: (BuildContext context, int index) {
-                    return Container(
+                    return SizedBox(
                       height: 100,
                       child: Text('item ${items[index]}'),
                     );
@@ -63,7 +63,7 @@ void main() {
                     });
                   },
                   itemBuilder: (BuildContext context, int index) {
-                    return Container(
+                    return SizedBox(
                       height: 100,
                       child: Text('item ${items[index]}'),
                     );

packages/flutter/test/widgets/reparent_state_test.dart

@@ -205,7 +205,7 @@ void main() {
         child: ListView(
           itemExtent: 100.0,
           children: <Widget>[
-            Container(
+            SizedBox(
               key: const Key('container'),
               height: 100.0,
               child: StateMarker(key: key),
@@ -279,7 +279,7 @@ void main() {
     await tester.pumpWidget(Stack(
       textDirection: TextDirection.ltr,
       children: <Widget>[
-        Container(width: 100.0, height: 100.0, child: StateMarker(key: key)),
+        SizedBox(width: 100.0, height: 100.0, child: StateMarker(key: key)),
         const SizedBox(width: 100.0, height: 100.0),
       ],
     ));
@@ -303,7 +303,7 @@ void main() {
       textDirection: TextDirection.ltr,
       children: <Widget>[
         const SizedBox(width: 100.0, height: 100.0),
-        Container(width: 100.0, height: 100.0, child: StateMarker(key: key)),
+        SizedBox(width: 100.0, height: 100.0, child: StateMarker(key: key)),
       ],
     ));
 

packages/flutter/test/widgets/row_test.dart

@@ -46,9 +46,9 @@ void main() {
       child: Row(
         key: rowKey,
         children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
-          Expanded(child: Container(key: child1Key, width: 100.0, height: 100.0, child: log(2))),
-          Container(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
+          SizedBox(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
+          Expanded(child: SizedBox(key: child1Key, width: 100.0, height: 100.0, child: log(2))),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
         ],
       ),
     ));
@@ -77,9 +77,9 @@ void main() {
       child: Row(
         key: rowKey,
         children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
-          Container(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
-          Container(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
+          SizedBox(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
         ],
       ),
     ));
@@ -108,8 +108,8 @@ void main() {
         key: rowKey,
         mainAxisAlignment: MainAxisAlignment.center,
         children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
-          Container(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
+          SizedBox(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
         ],
       ),
     ));
@@ -139,9 +139,9 @@ void main() {
         key: rowKey,
         mainAxisAlignment: MainAxisAlignment.end,
         children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
-          Container(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
-          Container(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
+          SizedBox(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
         ],
       ),
     ));
@@ -171,9 +171,9 @@ void main() {
         key: rowKey,
         mainAxisAlignment: MainAxisAlignment.spaceBetween,
         children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
-          Container(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
-          Container(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
+          SizedBox(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
         ],
       ),
     ));
@@ -204,10 +204,10 @@ void main() {
         key: rowKey,
         mainAxisAlignment: MainAxisAlignment.spaceAround,
         children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
-          Container(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
-          Container(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
-          Container(key: child3Key, width: 100.0, height: 100.0, child: log(4)),
+          SizedBox(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
+          SizedBox(key: child3Key, width: 100.0, height: 100.0, child: log(4)),
         ],
       ),
     ));
@@ -237,9 +237,9 @@ void main() {
         key: rowKey,
         mainAxisAlignment: MainAxisAlignment.spaceEvenly,
         children: <Widget>[
-          Container(key: child0Key, width: 200.0, height: 100.0, child: log(1)),
-          Container(key: child1Key, width: 200.0, height: 100.0, child: log(2)),
-          Container(key: child2Key, width: 200.0, height: 100.0, child: log(3)),
+          SizedBox(key: child0Key, width: 200.0, height: 100.0, child: log(1)),
+          SizedBox(key: child1Key, width: 200.0, height: 100.0, child: log(2)),
+          SizedBox(key: child2Key, width: 200.0, height: 100.0, child: log(3)),
         ],
       ),
     ));
@@ -268,8 +268,8 @@ void main() {
         key: rowKey,
         mainAxisSize: MainAxisSize.min,
         children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
-          Container(key: child1Key, width: 150.0, height: 100.0, child: log(2)),
+          SizedBox(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
+          SizedBox(key: child1Key, width: 150.0, height: 100.0, child: log(2)),
         ],
       ),
     ));
@@ -285,14 +285,14 @@ void main() {
     const Key childKey = Key('childKey');
 
     await tester.pumpWidget(Center(
-      child: Container(
+      child: SizedBox(
         width: 0.0,
         height: 0.0,
         child: Row(
           mainAxisSize: MainAxisSize.min,
           mainAxisAlignment: MainAxisAlignment.center,
-          children: <Widget>[
-            Container(
+          children: const <Widget>[
+            SizedBox(
               key: childKey,
               width: 100.0,
               height: 100.0,
@@ -325,9 +325,9 @@ void main() {
         key: rowKey,
         textDirection: TextDirection.ltr,
         children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
-          Expanded(child: Container(key: child1Key, width: 100.0, height: 100.0, child: log(2))),
-          Container(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
+          SizedBox(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
+          Expanded(child: SizedBox(key: child1Key, width: 100.0, height: 100.0, child: log(2))),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
         ],
       ),
     ));
@@ -375,9 +375,9 @@ void main() {
         key: rowKey,
         textDirection: TextDirection.ltr,
         children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
-          Container(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
-          Container(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
+          SizedBox(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
         ],
       ),
     ));
@@ -424,8 +424,8 @@ void main() {
         mainAxisAlignment: MainAxisAlignment.center,
         textDirection: TextDirection.ltr,
         children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
-          Container(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
+          SizedBox(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
         ],
       ),
     ));
@@ -467,9 +467,9 @@ void main() {
         textDirection: TextDirection.ltr,
         mainAxisAlignment: MainAxisAlignment.end,
         children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
-          Container(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
-          Container(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
+          SizedBox(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
         ],
       ),
     ));
@@ -517,9 +517,9 @@ void main() {
         mainAxisAlignment: MainAxisAlignment.spaceBetween,
         textDirection: TextDirection.ltr,
         children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
-          Container(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
-          Container(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
+          SizedBox(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
         ],
       ),
     ));
@@ -568,10 +568,10 @@ void main() {
         mainAxisAlignment: MainAxisAlignment.spaceAround,
         textDirection: TextDirection.ltr,
         children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
-          Container(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
-          Container(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
-          Container(key: child3Key, width: 100.0, height: 100.0, child: log(4)),
+          SizedBox(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
+          SizedBox(key: child3Key, width: 100.0, height: 100.0, child: log(4)),
         ],
       ),
     ));
@@ -625,9 +625,9 @@ void main() {
         mainAxisAlignment: MainAxisAlignment.spaceEvenly,
         textDirection: TextDirection.ltr,
         children: <Widget>[
-          Container(key: child0Key, width: 200.0, height: 100.0, child: log(1)),
-          Container(key: child1Key, width: 200.0, height: 100.0, child: log(2)),
-          Container(key: child2Key, width: 200.0, height: 100.0, child: log(3)),
+          SizedBox(key: child0Key, width: 200.0, height: 100.0, child: log(1)),
+          SizedBox(key: child1Key, width: 200.0, height: 100.0, child: log(2)),
+          SizedBox(key: child2Key, width: 200.0, height: 100.0, child: log(3)),
         ],
       ),
     ));
@@ -674,8 +674,8 @@ void main() {
         mainAxisSize: MainAxisSize.min,
         textDirection: TextDirection.ltr,
         children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
-          Container(key: child1Key, width: 150.0, height: 100.0, child: log(2)),
+          SizedBox(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
+          SizedBox(key: child1Key, width: 150.0, height: 100.0, child: log(2)),
         ],
       ),
     ));
@@ -707,15 +707,15 @@ void main() {
     const Key childKey = Key('childKey');
 
     await tester.pumpWidget(Center(
-      child: Container(
+      child: SizedBox(
         width: 0.0,
         height: 0.0,
         child: Row(
           textDirection: TextDirection.ltr,
           mainAxisSize: MainAxisSize.min,
           mainAxisAlignment: MainAxisAlignment.center,
-          children: <Widget>[
-            Container(
+          children: const <Widget>[
+            SizedBox(
               key: childKey,
               width: 100.0,
               height: 100.0,
@@ -748,9 +748,9 @@ void main() {
         key: rowKey,
         textDirection: TextDirection.rtl,
         children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
-          Expanded(child: Container(key: child1Key, width: 100.0, height: 100.0, child: log(2))),
-          Container(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
+          SizedBox(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
+          Expanded(child: SizedBox(key: child1Key, width: 100.0, height: 100.0, child: log(2))),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
         ],
       ),
     ));
@@ -798,9 +798,9 @@ void main() {
         key: rowKey,
         textDirection: TextDirection.rtl,
         children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
-          Container(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
-          Container(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
+          SizedBox(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
         ],
       ),
     ));
@@ -847,8 +847,8 @@ void main() {
         mainAxisAlignment: MainAxisAlignment.center,
         textDirection: TextDirection.rtl,
         children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
-          Container(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
+          SizedBox(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
         ],
       ),
     ));
@@ -890,9 +890,9 @@ void main() {
         textDirection: TextDirection.rtl,
         mainAxisAlignment: MainAxisAlignment.end,
         children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
-          Container(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
-          Container(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
+          SizedBox(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
         ],
       ),
     ));
@@ -940,9 +940,9 @@ void main() {
         mainAxisAlignment: MainAxisAlignment.spaceBetween,
         textDirection: TextDirection.rtl,
         children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
-          Container(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
-          Container(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
+          SizedBox(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
         ],
       ),
     ));
@@ -991,10 +991,10 @@ void main() {
         mainAxisAlignment: MainAxisAlignment.spaceAround,
         textDirection: TextDirection.rtl,
         children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
-          Container(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
-          Container(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
-          Container(key: child3Key, width: 100.0, height: 100.0, child: log(4)),
+          SizedBox(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
+          SizedBox(key: child1Key, width: 100.0, height: 100.0, child: log(2)),
+          SizedBox(key: child2Key, width: 100.0, height: 100.0, child: log(3)),
+          SizedBox(key: child3Key, width: 100.0, height: 100.0, child: log(4)),
         ],
       ),
     ));
@@ -1048,9 +1048,9 @@ void main() {
         mainAxisAlignment: MainAxisAlignment.spaceEvenly,
         textDirection: TextDirection.rtl,
         children: <Widget>[
-          Container(key: child0Key, width: 200.0, height: 100.0, child: log(1)),
-          Container(key: child1Key, width: 200.0, height: 100.0, child: log(2)),
-          Container(key: child2Key, width: 200.0, height: 100.0, child: log(3)),
+          SizedBox(key: child0Key, width: 200.0, height: 100.0, child: log(1)),
+          SizedBox(key: child1Key, width: 200.0, height: 100.0, child: log(2)),
+          SizedBox(key: child2Key, width: 200.0, height: 100.0, child: log(3)),
         ],
       ),
     ));
@@ -1097,8 +1097,8 @@ void main() {
         mainAxisSize: MainAxisSize.min,
         textDirection: TextDirection.rtl,
         children: <Widget>[
-          Container(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
-          Container(key: child1Key, width: 150.0, height: 100.0, child: log(2)),
+          SizedBox(key: child0Key, width: 100.0, height: 100.0, child: log(1)),
+          SizedBox(key: child1Key, width: 150.0, height: 100.0, child: log(2)),
         ],
       ),
     ));
@@ -1130,15 +1130,15 @@ void main() {
     const Key childKey = Key('childKey');
 
     await tester.pumpWidget(Center(
-      child: Container(
+      child: SizedBox(
         width: 0.0,
         height: 0.0,
         child: Row(
           textDirection: TextDirection.rtl,
           mainAxisSize: MainAxisSize.min,
           mainAxisAlignment: MainAxisAlignment.center,
-          children: <Widget>[
-            Container(
+          children: const <Widget>[
+            SizedBox(
               key: childKey,
               width: 100.0,
               height: 100.0,

packages/flutter/test/widgets/scroll_activity_test.dart

@@ -8,7 +8,7 @@ import 'package:flutter_test/flutter_test.dart';
 
 List<Widget> children(int n) {
   return List<Widget>.generate(n, (int i) {
-    return Container(height: 100.0, child: Text('$i'));
+    return SizedBox(height: 100.0, child: Text('$i'));
   });
 }
 

packages/flutter/test/widgets/scroll_controller_test.dart

@@ -17,7 +17,7 @@ void main() {
         child: ListView(
           controller: controller,
           children: kStates.map<Widget>((String state) {
-            return Container(
+            return SizedBox(
               height: 200.0,
               child: Text(state),
             );
@@ -56,7 +56,7 @@ void main() {
           key: const Key('second'),
           controller: controller,
           children: kStates.map<Widget>((String state) {
-            return Container(
+            return SizedBox(
               height: 200.0,
               child: Text(state),
             );
@@ -82,7 +82,7 @@ void main() {
           key: const Key('second'),
           controller: controller2,
           children: kStates.map<Widget>((String state) {
-            return Container(
+            return SizedBox(
               height: 200.0,
               child: Text(state),
             );
@@ -106,7 +106,7 @@ void main() {
           controller: controller2,
           physics: const BouncingScrollPhysics(),
           children: kStates.map<Widget>((String state) {
-            return Container(
+            return SizedBox(
               height: 200.0,
               child: Text(state),
             );
@@ -213,7 +213,7 @@ void main() {
               child: ListView(
                 controller: controller,
                 children: kStates.map<Widget>((String state) {
-                  return Container(height: 200.0, child: Text(state));
+                  return SizedBox(height: 200.0, child: Text(state));
                 }).toList(),
               ),
             ),
@@ -222,7 +222,7 @@ void main() {
               child: ListView(
                 controller: controller,
                 children: kStates.map<Widget>((String state) {
-                  return Container(height: 200.0, child: Text(state));
+                  return SizedBox(height: 200.0, child: Text(state));
                 }).toList(),
               ),
             ),
@@ -253,7 +253,7 @@ void main() {
               child: ListView(
                 controller: controller,
                 children: kStates.map<Widget>((String state) {
-                  return Container(height: 200.0, child: Text(state));
+                  return SizedBox(height: 200.0, child: Text(state));
                 }).toList(),
               ),
             ),
@@ -262,7 +262,7 @@ void main() {
               child: ListView(
                 controller: controller,
                 children: kStates.map<Widget>((String state) {
-                  return Container(height: 200.0, child: Text(state));
+                  return SizedBox(height: 200.0, child: Text(state));
                 }).toList(),
               ),
             ),
@@ -291,7 +291,7 @@ void main() {
         child: ListView(
           controller: controller,
           children: kStates.map<Widget>((String state) {
-            return Container(height: 200.0, child: Text(state));
+            return SizedBox(height: 200.0, child: Text(state));
           }).toList(),
         ),
       ),
@@ -324,7 +324,7 @@ void main() {
               key: UniqueKey(), // it's a different ListView every time
               controller: controller,
               children: List<Widget>.generate(50, (int index) {
-                return Container(height: 100.0, child: Text('Item $index'));
+                return SizedBox(height: 100.0, child: Text('Item $index'));
               }).toList(),
             ),
           ),
@@ -339,18 +339,18 @@ void main() {
     // scroll offset.
     ScrollController controller = ScrollController(initialScrollOffset: 200.0);
     await tester.pumpWidget(buildFrame(controller));
-    expect(tester.getTopLeft(find.widgetWithText(Container, 'Item 2')), Offset.zero);
+    expect(tester.getTopLeft(find.widgetWithText(SizedBox, 'Item 2')), Offset.zero);
 
     controller.jumpTo(2000.0);
     await tester.pump();
-    expect(tester.getTopLeft(find.widgetWithText(Container, 'Item 20')), Offset.zero);
+    expect(tester.getTopLeft(find.widgetWithText(SizedBox, 'Item 20')), Offset.zero);
 
     // The initialScrollOffset isn't used in this case, because the scrolloffset
     // can be restored.
     controller = ScrollController(initialScrollOffset: 25.0);
     await tester.pumpWidget(buildFrame(controller));
     expect(controller.offset, 2000.0);
-    expect(tester.getTopLeft(find.widgetWithText(Container, 'Item 20')), Offset.zero);
+    expect(tester.getTopLeft(find.widgetWithText(SizedBox, 'Item 20')), Offset.zero);
 
     // keepScrollOffset: false. The scroll offset is -not- restored
     // when the ListView is recreated with a new ScrollController and
@@ -359,7 +359,7 @@ void main() {
     controller = ScrollController(keepScrollOffset: false, initialScrollOffset: 100.0);
     await tester.pumpWidget(buildFrame(controller));
     expect(controller.offset, 100.0);
-    expect(tester.getTopLeft(find.widgetWithText(Container, 'Item 1')), Offset.zero);
+    expect(tester.getTopLeft(find.widgetWithText(SizedBox, 'Item 1')), Offset.zero);
 
   });
 }

packages/flutter/test/widgets/scroll_view_test.dart

@@ -851,7 +851,7 @@ void main() {
           child: ListView(
             controller: controller,
             children: kStates.map<Widget>((String state) {
-              return Container(
+              return SizedBox(
                 height: 200.0,
                 child: Text(state),
               );