anchor.diff:          expectAsync0(() {
             expect(machine.current, stateB);
             stateC.enter();
  -        }) as Callback0);
  +        }));
   
       machine.start();
     });
  
positive.code:           expect(machine.current, stateA);
            log.add('a');
            stateB.enter();
          }) as Callback1);
      stateB.onFuture(
          new Future.delayed(new Duration(milliseconds: 1)),
          expectAsync1((value) {
            expect(log, ['a']);
            expect(value, isNull);
          }) as Callback1);
  
      machine.start();
    });
  
negative.code:         expectAsync0(() {
            expect(machine.current, stateA);
            stateB.enter();
          }));
      stateA.onTimeout(
          new Duration(milliseconds: 20),
          () => fail('should never be called'));
  