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