Mockito http.Client 类型 'Null' 不是类型转换中类型 'Future<Response>' 的子类型

Question

我正在使用 Mockito 对 Flutter 应用程序中的 http 请求进行单元测试。

待测代码：

@GenerateMocks([http.Client])
void main() {
  late GdprDataSourceImpl dataSource;
  late MockClient mockHttpClient;

  setUp(() {
    mockHttpClient = MockClient();
    dataSource = GdprDataSourceImpl(
      httpClient: mockHttpClient,
      baseUrl: '',
    );
  });

  group('post Gdpr', () {
    const status = true;
    final url = Uri.parse('/gdpr/consent');

    const body = {
      'status': status,
    };

    final errorMessage = fixture('error_response.json');
    
    test('should perform a POST request to /auth/otp', () async {
      when(mockHttpClient.post(url, body: body)).thenAnswer(
        (_) async => http.Response('', 201),
      );

      await dataSource.postGdpr(status: status);

      verify(mockHttpClient.post(url, body: body));
    });
  });
}

我收到以下错误： type 'Null' 不是类型 cast

中类型 'Future' 的子类型

已使用构建运行程序成功生成模拟

我还尝试更新模拟的 class 并将 return 值更改为

returnValue: Future<http.Response?>

我得到：type 'Future<Response?>' is not a subtype of type 'Future' in type cast

Answer 1

所以解决方案是使用 package:http 提供的 MockClient class，并且不使用 mockito。

  group('post Gdpr success', () {
    Future<http.Response> requestHandler(http.Request request) async {
      final apiResponse = fixture('gdpr_response.json');
      return http.Response(apiResponse, 201);
    }

    setUp(() {
      mockHttpClient = MockClient(requestHandler);

      dataSource = GdprDataSourceImpl(
        httpClient: mockHttpClient,
        baseUrl: '',
      );
    });

    test('should perform a POST request to /gdpr/consent', () async {
      final result = await dataSource.postGdpr(status: status);
      expect(result, gdprResponse);
    });
  });

Mockito http.Client 类型 'Null' 不是类型转换中类型 'Future<Response>' 的子类型

Mockito http.Client type 'Null' is not a subtype of type 'Future<Response>' in type cast

unit-testing

mockito

dart

flutter