Typescript 将 TypeORM 存储库注入 NestJS 服务以进行模拟数据测试

假设我们有一个非常简单的服务，它通过id查找用户实体:

export class UserService {
  constructor(@InjectRepository(UserEntity) private userRepository: Repository<UserEntity>) {
  }

  async findUser(userId: string): Promise<UserEntity> {
    return this.userRepository.findOne(userId);
  }
}

然后，您可以使用以下模拟工厂模拟UserRepository(根据需要添加更多方法):

// @ts-ignore
export const repositoryMockFactory: () => MockType<Repository<any>> = jest.fn(() => ({
  findOne: jest.fn(entity => entity),
  // ...
}));

使用工厂可以确保每次测试都使用新的模拟.

describe('UserService', () => {
  let service: UserService;
  let repositoryMock: MockType<Repository<UserEntity>>;

  beforeEach(async () => {
    const module: TestingModule = await Test.createTestingModule({
      providers: [
        UserService,
        // Provide your mock instead of the actual repository
        { provide: getRepositoryToken(UserEntity), useFactory: repositoryMockFactory },
      ],
    }).compile();
    service = module.get<UserService>(UserService);
    repositoryMock = module.get(getRepositoryToken(UserEntity));
  });

  it('should find a user', async () => {
    const user = {name: 'Alni', id: '123'};
    // Now you can control the return value of your mock's methods
    repositoryMock.findOne.mockReturnValue(user);
    expect(service.findUser(user.id)).toEqual(user);
    // And make assertions on how often and with what params your mock's methods are called
    expect(repositoryMock.findOne).toHaveBeenCalledWith(user.id);
  });
});

为了确保键入的安全性和舒适性，您可以在(部分)模拟中使用以下键入(远不是完美的，当jest本身在即将发布的主要版本中开始使用typescript时，可能会有更好的解决方案):

export type MockType<T> = {
  [P in keyof T]?: jest.Mock<{}>;
};