假设我们有一个非常简单的服务，该服务通过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
UserRepository使用以下模拟工厂模拟（根据需要添加更多方法）：
// @ts-ignoreexport const repositoryMockFactory: () => MockType<Repository<any>> = jest.fn(() => ({ findOne: jest.fn(entity => entity), // ...}));使用工厂可确保为每个测试使用新的模拟。
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); });});为了确保类型安全和舒适，您可以在模拟中使用以下类型（远非完美，当笑话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<{}>;};
