LibTest/async/Stream/Stream.periodic_A01_t01.dart

/*
 * Copyright (c) 2011, 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.
 */
/**
 * @assertion factory Stream.periodic(Duration period, [T computation(int computationCount)])
 * Creates a stream that repeatedly emits events at period intervals.
 * If computation is omitted the event values will all be null.
 * @description Checks that created stream emits events at period intervals.
 * Checks that if computation is omitted the event value is null.
 * @author kaigorodov
 */

import "dart:async";
import "../../../Utils/async_utils.dart";
import "../../../Utils/expect.dart";

check(int periodMs) {
  Duration period=durationMs(periodMs);
  const maxCount=5;
  int count=0;

  Stopwatch sw=new Stopwatch();
  sw.start();
  
  asyncStart();
  
  Stream s=new Stream.periodic(period);

  var subs = s.listen(null);
  subs.onData((int event) {
    count++;
    Expect.isNull(event, "onData");
    Duration expected=period*count;
    Duration actual=sw.elapsed;
    Expect.isTrue(expected<=actual, "expected=$expected, actual=$actual");
    //print('expected=$expected actual=$actual');
    if (count>=maxCount) {
      subs.cancel();
      asyncEnd();
    }
  });
}

main() {
  check(0);
  check(1);
  check(10);
  check(30);
  check(100);
}