dart-sdk/tests/lib_2/async/timer_repeat_test.dart

// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

// @dart = 2.9

library timer_repeat_test;

import 'dart:async';

import 'package:expect/expect.dart';

const Duration TIMEOUT = const Duration(milliseconds: 500);
const int ITERATIONS = 5;

Timer timer;
Stopwatch stopwatch = new Stopwatch();
int iteration;

// Some browsers (Firefox and IE so far) can trigger too early. Add a safety
// margin. We use identical(1, 1.0) as an easy way to know if the test is
// compiled by dart2js.
int get safetyMargin => identical(1, 1.0) ? 100 : 0;

var completer = new Completer();

void timeoutHandler(Timer timer) {
  iteration++;
  Expect.isTrue(iteration <= ITERATIONS);
  if (iteration == ITERATIONS) {
    // When we are done with all of the iterations, we expect a
    // certain amount of time to have passed.  Checking the time on
    // each iteration doesn't work because the timeoutHandler runs
    // concurrently with the periodic timer.
    Expect.isTrue(stopwatch.elapsedMilliseconds + safetyMargin >=
        ITERATIONS * TIMEOUT.inMilliseconds);
    timer.cancel();
    completer.complete();
  }
}

main() {
  iteration = 0;
  stopwatch.start();
  timer = new Timer.periodic(TIMEOUT, timeoutHandler);
  return completer.future;
}