Flutter: BLoC, testing streams

Testing the bloc pattern is not so clear to me. So, if I have these 2 stream controllers:

final _controller1 = StreamController();
final _controller2 = StreamController<bool>;

Stream<bool> get controller2Out = _controller2.stream;

and I want to test that, from this function:

submit() {
if (_controller1.value == null ||
        _controller1.value.isEmpty) {
          print(...)
      return;
    }else
       _controller2.sink.add(true);
    }

the _controller2.stream should have true, how should I do?

I tried something like:

  test("test", (){
    bloc.submit();
    expect(bloc.controller2Out, emitsAnyOf([true]));
  });

but, of course, it didn´t work.