如何测试Flutter Bloc测试中的异常

Question

我正在尝试使用Flutter中的Bloc_test框架编写BLOC测试。在任何人尝试将其删除之前，没有与测试小部件/单位测试进行扑来的例外情况。集体测试不同。

我有一个我正在测试的肘。它具有称为getPrinterforms（）的方法。我正在尝试测试被捕获的异常，以确保它发出正确的状态。谁能查看我的测试的代码以及该方法的代码，让我知道我是否做错了什么？

@GenerateMocks([PrinterRepositoryImpl])
void main() {
  late MockPrinterRepositoryImpl mockPrinterRepository;
  late PrinterCubit printerCubit;

  setUp(() {
    mockPrinterRepository = MockPrinterRepositoryImpl();
    printerCubit = PrinterCubit(mockPrinterRepository);
  });

  tearDown(() {
    printerCubit.close();
  });

  group('PrinterCubit Tests', () {
        blocTest(
      'getPrinterForms emits [PrinterLoading, PrinterError] when unsuccessful',
      build: () {
        when(mockPrinterRepository.fetchPrinterForms(http.Client())).thenThrow(NetworkException());
        return printerCubit;
      },
      act: (PrinterCubit cubit) => cubit.getPrinterForms(),
      expect: () => [
        PrinterLoading(),
        const PrinterError("Couldn't fetch printer forms. Is the device online?")
      ],
    );
  });
}



class NetworkException implements Exception{}

  Future<void> getPrinterForms() async {
    try {
      emit(PrinterLoading());
      final printerForms = await _printerRepository.fetchPrinterForms(http.Client());
      emit(PrinterLoaded(printerForms));
    } on NetworkException {
      emit(const PrinterError("Couldn't fetch printer forms. Is the device online?"));
    }    
  }

@override
abstract class PrinterState extends Equatable {
  const PrinterState();
  
  @override
  List<Object> get props => [];
}

class PrinterInitial extends PrinterState {}

class PrinterLoading extends PrinterState {}

class PrinterLoaded extends PrinterState {
  final List<PrinterModel> printerForms;
  const PrinterLoaded(this.printerForms);
}

class PrinterDetails extends PrinterState {
  final PrinterModel printerForm;
  const PrinterDetails(this.printerForm);
}

class PrinterError extends PrinterState {
  final String message;
  const PrinterError(this.message);
}

Answer 1

我尝试了一下，无法重现失败的测试。

@GenerateMocks([PrinterRepository])
void main() {
  late PrinterRepository mockPrinterRepository;

  setUp(() {
    mockPrinterRepository = MockPrinterRepository();
  });

  group('PrinterCubit Tests', () {
    blocTest(
      'emits [PrinterLoading, PrinterError] when unsuccessful',
      build: () {
        when(mockPrinterRepository.fetchPrinterForms())
            .thenThrow(NetworkException());
        return PrinterCubit(mockPrinterRepository);
      },
      act: (PrinterCubit cubit) => cubit.getPrinterForms(),
      expect: () => [
        PrinterLoading(),
        const PrinterError(
          "Couldn't fetch printer forms. Is the device online?",
        )
      ],
    );
  });
}

小熊看起来像这样：

class PrinterCubit extends Cubit<PrinterState> {
  PrinterCubit([PrinterRepository? printerRepository]) : super(PrinterInitial()) {
    _printerRepository = printerRepository ?? PrinterRepository();
  }

  late PrinterRepository _printerRepository;

  Future<void> getPrinterForms() async {
    try {
      emit(PrinterLoading());
      final printerForms = await _printerRepository.fetchPrinterForms();
      emit(PrinterLoaded(printerForms));
    } on NetworkException {
      emit(const PrinterError(
        "Couldn't fetch printer forms. Is the device online?",
      ));
    }
  }
}

class NetworkException implements Exception {}

class PrinterRepository {
  Future<List<PrinterModel>> fetchPrinterForms() async {
    return [PrinterModel("Samsung"), PrinterModel("HP")];
  }
}

class PrinterModel {
  PrinterModel(this.name);

  final String name;
}

00:01 +1: All tests passed!