在单元测试 Nest.js 中模拟注入服务

Question

我想测试我的服务（定位服务）。在这个位置服务中，我注入了存储库和其他名为 GeoLocationService 的服务，但是当我尝试模拟这个 GeoLocationService 时卡住了。

它给我一个错误

GeolocationService › should be defined

    Nest can't resolve dependencies of the GeolocationService (?). Please make sure that the argument HttpService at index [0] is available in the RootTestModule context.

这里是提供者的代码

@Injectable()
export class LocationService {
  constructor(
    @Inject('LOCATION_REPOSITORY')
    private locationRepository: Repository<Location>,

    private geolocationService: GeolocationService, // this is actually what I ma trying to mock
  ) {}

  async getAllLocations(): Promise<Object> {
return await this.locationRepository.find()
  }
....
}

这是测试代码

describe('LocationService', () => {
  let service: LocationService;
  let repo: Repository<Location>;

  beforeEach(async () => {
    const module: TestingModule = await Test.createTestingModule({
      imports: [GeolocationModule],
      providers: [
        LocationService,
        {
          provide: getRepositoryToken(Location),
          useClass: Repository,
        },
      ],
    }).compile();

    service = module.get<LocationService>(LocationService);
    repo = module.get<Repository<Location>>(getRepositoryToken(Location));
  });

  it('should be defined', () => {
    expect(service).toBeDefined();
  });
});

Answer 1

您应该提供GeolocationService 的模拟，而不是添加imports: [GeolocationModule]。这个模拟应该与GeolocationService 具有相同的方法名称，但它们都可以被存根（jest.fn()）或者它们可以有一些返回值（jest.fn().mockResolved/ReturnedValue()）。通常，自定义提供程序（添加到 providers 数组）如下所示：

{
  provide: GeolocationService,
  useValue: {
    method1: jest.fn(),
    method2: jest.fn(),
  }
}

You can find a large sample of mocks in this repository.