diff --git a/pkg/analysis_server/test/src/services/correction/fix/add_async_test.dart b/pkg/analysis_server/test/src/services/correction/fix/add_async_test.dart
index f4c17458dd4..185a29163a1 100644
--- a/pkg/analysis_server/test/src/services/correction/fix/add_async_test.dart
+++ b/pkg/analysis_server/test/src/services/correction/fix/add_async_test.dart
@@ -4,11 +4,11 @@
 
 import 'package:analysis_server/src/services/correction/fix.dart';
 import 'package:analysis_server/src/services/linter/lint_names.dart';
-import 'package:analyzer/src/dart/analysis/experiments.dart';
 import 'package:analyzer/src/error/codes.dart';
 import 'package:analyzer_plugin/utilities/fixes/fixes.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
+import '../../../../abstract_context.dart';
 import 'fix_processor.dart';
 
 void main() {
@@ -216,10 +216,8 @@ main() async {
 }
 
 @reflectiveTest
-class AddAsyncWithNullSafetyTest extends FixProcessorTest {
-  @override
-  List<String> get experiments => [EnableString.non_nullable];
-
+class AddAsyncWithNullSafetyTest extends FixProcessorTest
+    with WithNullSafetyMixin {
   @override
   FixKind get kind => DartFixKind.ADD_ASYNC;
 
diff --git a/pkg/analysis_server/test/src/services/correction/fix/fix_processor.dart b/pkg/analysis_server/test/src/services/correction/fix/fix_processor.dart
index 321da9d498e..0900c1b30ec 100644
--- a/pkg/analysis_server/test/src/services/correction/fix/fix_processor.dart
+++ b/pkg/analysis_server/test/src/services/correction/fix/fix_processor.dart
@@ -7,11 +7,9 @@ import 'package:analysis_server/src/services/correction/change_workspace.dart';
 import 'package:analysis_server/src/services/correction/fix.dart';
 import 'package:analysis_server/src/services/correction/fix/dart/top_level_declarations.dart';
 import 'package:analysis_server/src/services/correction/fix_internal.dart';
-import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/instrumentation/service.dart';
 import 'package:analyzer/src/dart/analysis/byte_store.dart';
-import 'package:analyzer/src/dart/analysis/experiments.dart';
 import 'package:analyzer/src/dart/error/lint_codes.dart';
 import 'package:analyzer/src/services/available_declarations.dart';
 import 'package:analyzer/src/test_utilities/platform.dart';
@@ -40,8 +38,11 @@ abstract class FixProcessorLintTest extends FixProcessorTest {
   }
 
   @override
-  void _createAnalysisOptionsFile() {
-    createAnalysisOptionsFile(experiments: experiments, lints: [lintCode]);
+  void setUp() {
+    super.setUp();
+    createAnalysisOptionsFile(
+      lints: [lintCode],
+    );
   }
 }
 
@@ -58,10 +59,6 @@ abstract class FixProcessorTest extends AbstractSingleUnitTest {
   /// neither [assertHasFix] nor [assertHasFixAllFix] has been invoked.
   String resultCode;
 
-  /// Return a list of the experiments that are to be enabled for tests in this
-  /// class, or `null` if there are no experiments that should be enabled.
-  List<String> get experiments => null;
-
   /// Return the kind of fixes being tested by this test class.
   FixKind get kind;
 
@@ -166,7 +163,6 @@ abstract class FixProcessorTest extends AbstractSingleUnitTest {
     super.setUp();
     verifyNoTestUnitErrors = false;
     useLineEndingsForPlatform = true;
-    _createAnalysisOptionsFile();
   }
 
   /// Computes fixes and verifies that there is a fix for the given [error] of the appropriate kind.
@@ -291,12 +287,6 @@ abstract class FixProcessorTest extends AbstractSingleUnitTest {
     return await DartFixContributor().computeFixes(context);
   }
 
-  /// Create the analysis options file needed in order to correctly analyze the
-  /// test file.
-  void _createAnalysisOptionsFile() {
-    createAnalysisOptionsFile(experiments: experiments);
-  }
-
   /// Find the error that is to be fixed by computing the errors in the file,
   /// using the [errorFilter] to filter out errors that should be ignored, and
   /// expecting that there is a single remaining error. The error filter should
@@ -349,16 +339,14 @@ mixin WithNullSafetyLintMixin on AbstractContextTest {
   String get lintCode;
 
   @override
-  String get testPackageLanguageVersion =>
-      Feature.non_nullable.isEnabledByDefault ? '2.12' : '2.11';
+  String get testPackageLanguageVersion => '2.12';
 
-  /// TODO(scheglov) https://github.com/dart-lang/sdk/issues/43837
-  /// Remove when Null Safety is enabled by default.
   @nonVirtual
   @override
   void setUp() {
     super.setUp();
     createAnalysisOptionsFile(
-        experiments: [EnableString.non_nullable], lints: [lintCode]);
+      lints: [lintCode],
+    );
   }
 }
diff --git a/pkg/analysis_server/test/src/services/correction/fix/remove_dead_code_test.dart b/pkg/analysis_server/test/src/services/correction/fix/remove_dead_code_test.dart
index 62618ace612..3fd394ea84f 100644
--- a/pkg/analysis_server/test/src/services/correction/fix/remove_dead_code_test.dart
+++ b/pkg/analysis_server/test/src/services/correction/fix/remove_dead_code_test.dart
@@ -3,10 +3,10 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:analysis_server/src/services/correction/fix.dart';
-import 'package:analyzer/src/dart/analysis/experiments.dart';
 import 'package:analyzer_plugin/utilities/fixes/fixes.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
+import '../../../../abstract_context.dart';
 import 'fix_processor.dart';
 
 void main() {
@@ -140,10 +140,8 @@ int main() {
 }
 
 @reflectiveTest
-class RemoveDeadCodeWithNullSafetyTest extends FixProcessorTest {
-  @override
-  List<String> get experiments => [EnableString.non_nullable];
-
+class RemoveDeadCodeWithNullSafetyTest extends FixProcessorTest
+    with WithNullSafetyMixin {
   @override
   FixKind get kind => DartFixKind.REMOVE_DEAD_CODE;