Flutter 测试表明 bloc 没有产生任何状态

Question

I have a case when some condition is met, then the bloc is not yielding a state at all (ignoring all events). How can I test that no state is yielded when a new event is added to bloc ?

I'm using flutter_bloc: ^3.1.0 and bloc_test: ^3.1.0

      'test ignore all event after AlarmEvent()',
      () async {
        bloc.add(AlarmEvent());
        bloc.add(GetRandomPostEvent());

        await emitsExactly(
          bloc,
          [
            SplashScreenLoadingState(),
            ShowAlarmState(),
          ],
        );
      },
    );

As the feature is not implemented yet I'm expecting the test to fail but actually is runs successfully. Any idea ?

Answer 1

You can make a test specifically for that condition that nothing should be emitted, and subscribe to your bloc, then call fail() in the subscription if the block emits, so you know they only way the test succeeded is if fail() wasn't called. This should be a synchronous call as well.

Something like:

var subscription = myBlocStream.listen((_) { 
  fail('Should not emit'); 
}); 
myBloc.doSomething();
subscription.cancel();