findAll()函数单元测试报错：expect深度相等匹配失败

错误现象 #

执行findAll()函数单元测试时，UsersService和UsersController的findAll测试用例均失败，测试结果显示收到空对象，与预期的用户对象不匹配，触发expect(received).toEqual(expected) // deep equality断言错误。

错误详情 #

PASS  src/app.controller.spec.ts
FAIL  src/users/services/users.service.spec.ts
● UsersService › should return all users
expect(received).toEqual(expected) // deep equality
- Expected  - 6
+ Received  + 1
- Object {
-   "birthDate": 2010-06-07T00:00:00.000Z,
-   "email": "xs@gsuj.lk",
-   "id": 2,
-   "name": "aq1s",
- }
+ Object {}
  at src/users/services/users.service.spec.ts:68:38

FAIL  src/users/controllers/users.controller.spec.ts (5.09 s)
● UsersController › should findall
expect(received).toEqual(expected) // deep equality
- Expected  - 6
+ Received  + 1
- Object {
-   "birthDate": 2010-06-07T00:00:00.000Z,
-   "email": "xs@gsuj.lk",
-   "id": 2,
-   "name": "aq1s",
- }
+ Object {}
  at src/users/controllers/users.controller.spec.ts:131:18

测试套件统计：3个失败，1个通过，共4个；测试用例：2个失败，9个通过，共11个。

相关代码 #

Users.controller.spec.ts #

describe('UsersController', () => {
  let controller: UsersController;

  const mockUsersService = {
    create: jest.fn((dto) => {
      return {
        ...dto,
      };
    }),
    update: jest.fn((id, dto) => ({
      id,
      ...dto,
    })),
    delete: jest.fn((id) => ({
      id,
    })),
    findAll: jest.fn((dto) => {
      return {
        ...dto,
      };
    }),
  };

  beforeEach(async () => {
    const module: TestingModule = await Test.createTestingModule({
      controllers: [UsersController],
      providers: [UsersService],
    })
      .overrideProvider(UsersService)
      .useValue(mockUsersService)
      .compile();

    controller = module.get<UsersController>(UsersController);
  });

  it('should findall', async () => {
    const dto = {
      id: 2,
      name: 'aq1s',
      birthDate: new Date('2010-06-07'),
      email: 'xs@gsuj.lk',
    };

    const data = await controller.findAll();

    expect(data).toEqual({
      id: dto.id,
      name: dto.name,
      birthDate: dto.birthDate,
      email: dto.email,
    });
  });
});

user.service.spec.ts #

describe('UsersService', () => {
  let service: UsersService;

const mockUsersRepository ={
  create:jest.fn().mockImplementation(dto =>dto),
  save:jest.fn().mockImplementation(user => Promise.resolve({id:2, ...user})),
  find:jest.fn().mockImplementation(() => ({})),
}

  beforeEach(async () => {
    const module: TestingModule = await Test.createTestingModule({
      providers: [UsersService, {
        provide:getRepositoryToken(User),
        useValue:mockUsersRepository,
      },
    ],
    }).compile();

    service = module.get<UsersService>(UsersService);
  });

  it('should return all users', async () => {
    expect( await service.findAll()).toEqual({
       id:2, 
       name:'aq1s',
       birthDate: new Date('2010-06-07'), 
       email : "xs@gsuj.lk" , 
     });
   });
});

users.service.ts #

findAll(): Promise<User[]> {
   return this.userRepository.find()
 }

users.controller.ts #

@Get()
async findAll() {
  const users = await this.userService.findAll();
  if (!users) {
    return 'error while finding users';
  }
  return users;
}

问题分析与修复方案 #

1. 返回值类型不匹配：UsersService的findAll定义返回Promise<User[]>（用户数组），但测试用例期望单个用户对象。

   • 修复：将测试用例中的预期值改为数组格式，比如expect(await service.findAll()).toEqual([{ id:2, name:'aq1s', ... }])；同时确认Controller层的返回逻辑符合数组返回的预期。

2. Mock仓库返回值错误：mockUsersRepository的find方法返回空对象{}，实际应返回用户数组。

   • 修复：修改mock的find方法，返回包含预期用户的数组：

     find: jest.fn().mockImplementation(() => Promise.resolve([{
       id:2, 
       name:'aq1s',
       birthDate: new Date('2010-06-07'), 
       email : "xs@gsuj.lk" 
     }])),
     

3. Controller测试中Mock服务未正确返回数据：UsersController测试里的mockUsersService.findAll方法依赖传入的dto参数，但实际调用时无传参，导致返回空对象{}。

   • 修复：修改mockUsersService的findAll方法，直接返回预期的用户数组，无需依赖参数：

     findAll: jest.fn(() => {
       return [{
         id: 2,
         name: 'aq1s',
         birthDate: new Date('2010-06-07'),
         email: 'xs@gsuj.lk',
       }];
     }),
     

内容的提问来源于stack exchange，提问作者thi_m