anchor.diff:  
     group('elapseBlocking', () {
       test('should elapse time without calling timers', () {
  -      new Timer(elapseBy ~/ 2, neverCalled);
  +      new Timer(elapseBy ~/ 2, neverCalledVoid);
         new FakeAsync().elapseBlocking(elapseBy);
       });
   
  
positive.code: 
        test('should not call timers expiring after end time', () {
          new FakeAsync().run((async) {
            new Timer(elapseBy * 2, neverCalled);
            async.elapse(elapseBy);
          });
        });
  
        test('should not call canceled timers', () {
          new FakeAsync().run((async) {
            var timer = new Timer(elapseBy ~/ 2, neverCalled);
            timer.cancel();
            async.elapse(elapseBy);
          });
  
negative.code:     (actual) =>
          expected.difference(actual as DateTime).inMilliseconds.abs() < 100,
      "is close to $expected");
  
  /// A wrapper for [neverCalled] that works around sdk#33015.
  void Function() get neverCalledVoid {
    var function = neverCalled;
    return () => neverCalled();
  }
  