Widget Testing with Mocktail and Cubits

I cannot seem to get my widget test to work, and while the documentation does not specifically cover testing with state management, this issue (https://github.com/felangel/mocktail/issues/42) pretty much confirms that what I discerned seems to be correct, however, I keep running into the error

type 'Null' is not a subtype of type 'Stream<BulkUploadState>'.

class MockBulkUploadCubit extends Mock implements BulkUploadCubit {}

class FakeBulkUploadState extends Fake implements BulkUploadState {}

void main() {
  TestWidgetsFlutterBinding.ensureInitialized();

  late MockBulkUploadCubit mockCubit;

  setUpAll(() {
    registerFallbackValue<BulkUploadState>(FakeBulkUploadState());
  });

  setUp(() {
    mockCubit = MockBulkUploadCubit();
  });

  testWidgets(
    "BulkSearchInput",
    (tester) async {
      when(() => mockCubit.state).thenReturn(BulkUploadState.initial());

      await tester.pumpWidget(
        BlocProvider<BulkUploadCubit>.value(
          value: mockCubit,
          child: const MaterialApp(home: BulkSearchInput()),
        ),
      );
      await tester.pumpAndSettle();
      expect(find.byType(TextFormField), findsOneWidget);
    },
  );
}

Currently pulling the state off context.select however when refactoring the widget to use BlocSelector I get the same error.

Not sure what I am missing here.