Nestjs Repository单元测试报错：Received promise resolved instead of rejected

问题背景 #

在为后端应用编写单元测试，测试数据库中不存在对应条目的场景时遇到问题。 #

待测试Repository代码 #

@EntityRepository(Collectible)
export class CollectibleRepository extends Repository<Collectible> {
  async getCollectible(id: number) {
    const collectible = await this.findOne(id);
    if (!collectible) {
      throw new NotFoundException();
    }
    return collectible;
  }
}

初始测试代码（出错用例） #

const mockCollectible = new Collectible(
  faker.lorem.sentence(),
  faker.lorem.sentences(3),
  faker.datatype.float(),
  faker.datatype.float(),
  faker.datatype.number(),
);

describe('Collectible Repository', () => {
  let collectibleRepository: CollectibleRepository;

  beforeEach(async () => {
    const module = await Test.createTestingModule({
      providers: [CollectibleRepository],
    }).compile();

    collectibleRepository = module.get<CollectibleRepository>(
      CollectibleRepository,
    );
  });

  describe('View Collectibles', () => {
       it('throws and error as the collectible is not found', async (done) => {
      collectibleRepository.findOne = jest.fn().mockResolvedValue(undefined);
      await expect(collectibleRepository.getCollectible(1)).rejects.toThrow(
        NotFoundException,
      );
      done();
    });
  });
});

首次运行报错信息 #

Expected message: not "Not Found"

       8 |     const collectible = await this.findOne(id, { relations: ['business'] });
       9 |     if (!collectible) {
    > 10 |       throw new NotFoundException();
         |             ^
      11 |     }
      12 |     return collectible;
      13 |   }

      at CollectibleRepository.getCollectibleBusiness (src/collectible/collectible.repository.ts:10:13)
(Use `node --trace-warnings ...` to show where the warning was created)
(node:95012) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict`. (rejection id: 3)
(node:95012) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
 FAIL  src/collectible/collectible.repository.spec.ts (8.525 s)
  ● Collectible Repository › View Collectibles › throws and error as the collectible is not found

    expect(received).rejects.not.toThrow()

    Received promise resolved instead of rejected
    Resolved to value: undefined

      39 |     it('throws and error as the collectible is not found', async (done) => {
      40 |       collectibleRepository.findOne = jest.fn().mockResolvedValue(undefined);
    > 41 |       await expect(collectibleRepository.getCollectible(1)).rejects.not.toThrow(
         |             ^
      42 |         NotFoundException,
      43 |       );
      44 |       done();

      at expect (../node_modules/expect/build/index.js:134:15)
      at Object.<anonymous> (collectible/collectible.repository.spec.ts:41:13)

排查与更新进展 #

• 首次排查参考NestJS测试示例仓库，未找到直接测试自定义Repository的相关内容
• 修正代码中缺失的await、调用错误函数的问题后，出现新警告：

(node:98378) UnhandledPromiseRejectionWarning: Error: expect(received).rejects.not.toThrow(expected)

• 后续确认该警告由其他测试用例导致，可暂时搁置

解决方案 #

核心错误原因 #

1. 断言逻辑写反：测试代码中多写了.not，原本预期抛出异常，错误写成了预期不抛出异常
2. 异步逻辑处理不当：混用async/await和done回调，导致异步异常没有被正确捕获

修正后测试用例 #

it('should throw NotFoundException when collectible does not exist', async () => {
  // 模拟findOne返回空，代表未查询到对应条目
  jest.spyOn(collectibleRepository, 'findOne').mockResolvedValue(undefined);
  // 直接断言方法会抛出NotFoundException
  await expect(collectibleRepository.getCollectible(1)).rejects.toThrow(NotFoundException);
});

优化建议 #

• 优先使用jest.spyOn模拟类方法，而非直接给方法赋值mock，方便后续恢复原方法实现
• 异步测试用例中不需要额外使用done回调，Jest会自动等待async函数的所有异步逻辑执行完成

内容的提问来源于stack exchange，提问作者Jeremy