anchor.diff:  
         test('should not call timers expiring after end time', () {
           new FakeAsync().run((async) {
  -          new Timer(elapseBy * 2, neverCalled);
  +          new Timer(elapseBy * 2, neverCalledVoid);
             async.elapse(elapseBy);
           });
         });
   
         test('should not call canceled timers', () {
           new FakeAsync().run((async) {
  -          var timer = new Timer(elapseBy ~/ 2, neverCalled);
  +          var timer = new Timer(elapseBy ~/ 2, neverCalledVoid);
             timer.cancel();
             async.elapse(elapseBy);
           });
  
positive.code: 
    group('elapseBlocking', () {
      test('should elapse time without calling timers', () {
        new Timer(elapseBy ~/ 2, neverCalled);
        new FakeAsync().elapseBlocking(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();
  }
  