anchor.diff:  
       stateA.onTimeout(
           new Duration(milliseconds: 10),
  -        expectAsync(() {
  +        expectAsync0(() {
             expect(machine.current, stateA);
             stateB.enter();
           }) as Callback0);
  
positive.code:         }) as Callback1);
      stateB.onFuture(
          new Future.delayed(new Duration(milliseconds: 1)),
          expectAsync((value) {
            expect(log, ['a']);
            expect(value, isNull);
          }) as Callback1);
  
negative.code:         (value) => fail('should never be called'));
      stateA.onFuture(
          new Future.delayed(new Duration(milliseconds: 10), () => 'something'),
          expectAsync1((value) {
            expect(log, isEmpty);
            expect(value, 'something');
            expect(machine.current, stateA);
  