testing - Flutter:如何模拟 Bloc

Question

我想模拟我的 Bloc 以测试我的观点。

例如，这是我的 Bloc:

class SearchBloc extends Bloc<SearchEvent, SearchState> {
  @override
  // TODO: implement initialState
  SearchState get initialState => SearchStateUninitialized();

  @override
  Stream<SearchState> mapEventToState(SearchState currentState, SearchEvent event) async* {
    if (event is UserWrites) {
      yield (SearchStateInitialized.success(objects);
    }
  }
}

这是 View :

class _SearchViewState extends State<SearchView> {
  final TextEditingController _filterController = new TextEditingController();

  @override
  void initState() {
    _filterController.addListener(() {
    widget._searchBloc.dispatch(FetchByName(_filterController.text));
     }
  }


 TextField buildAppBarTitle(BuildContext context) {
    return new TextField(
      key: Key("AppBarTextField"),
        controller: _filterController,
    );
  }

@override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: buildAppBarTitle(context),),
      body: buildBlocBuilder(),
    );
  }

BlocBuilder<SearchEvent, SearchState> buildBlocBuilder() {
    return BlocBuilder(
        bloc: widget._searchBloc,
        builder: (context, state) {
          if (state is SearchStateUninitialized) {
            return Container(
              key: Key("EmptyContainer"),
            );
          } 
            return buildInitializedView(state, context);
          }
        });

buildInitializedView(SearchStateInitialized state, BuildContext context) {
    if (state.objects.isEmpty) {
      return Center(child: Text("Nothing found"),);
    } else {
      return buildListOfCards();
    }
  }
    }

现在，这是我的测试:

testWidgets('Should find a card when the user searches for something', (WidgetTester tester) async {

  _searchView = new SearchView(_searchBloc);

    when(mockService.find( name: "a")).thenAnswer((_) =>
    [objects]);

    await tester.pumpWidget(generateApp(_searchView));
    await tester.enterText(find.byKey(Key("searchBar")), "a");
    await tester.pump();

    expect(find.byType(Card), findsOneWidget);
  });
}

如您所见，我只是想测试一下，当用户在搜索中输入内容并且他要查找的对象存在时，应该显示一张卡片。

Answer 1

如果我没理解错的话，您是在模拟 searchBloc 使用的某些服务。我个人尝试以一种方式设计应用程序，即应用程序仅依赖于一个 bloc，而 bloc 可能依赖于其他一些服务。然后当我想做一个小部件测试时，我只需要模拟这个 Bloc 。您可以为此使用 bloc_test 包。

在 bloc_test 页面上有这个用于 stub counterBloc 的示例:

// Create a mock instance
final counterBloc = MockCounterBloc();

// Stub the bloc `Stream`
whenListen(counterBloc, Stream.fromIterable([0, 1, 2, 3]));

然而，我通常不需要 stub bloc 流，它足以发出状态，就像这样

when(counterBloc.state).thenAnswer((_) => CounterState(456));

希望这对您有所帮助。