Tests fail when using @InjectRepository: Nest can't resolve Repository-CodePudding

I'm using NestJs with Typeorm, normal setup. UsersService gets the Typeorm Repository injected:

constructor(
    @InjectRepository(User)
    private usersRepository: Repository<User>,
  ) {}

In the UsersModule:

@Module({
  imports:[ TypeOrmModule.forFeature([User])],
  controllers: [UsersController ],
  providers: [UsersService]
})

Nothing special as you can see. But the auto-generated test for UsersService fails, no matter what I do:

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

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

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

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

I get the following error:

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

The solutions on Stackoverflow that I found seem to be obsolete, or over-complicated. I understand that the problem stems from the usage of @InjectRepository.

What is the solution? I tried downloading other people's fairly-similar projects, and get the same error! Both with nest 8 and 7.

CodePudding user response：

The docs are pretty clear on how to write tests when using @nestjs/typeorm: https://docs.nestjs.com/techniques/database#testing

There are a bunch of samples here as well: https://github.com/jmcdo29/testing-nestjs

CodePudding user response：

Nest can't resolve the dependency because you don't provide the repository in the testing module. If you're doing unit tests you probably want to mock the repository using a custom provider:

 import { getRepositoryToken } from '@nestjs/typeorm';

 describe('UsersService', () => {
   let service: UsersService;
   let repository: Repository<User>;

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

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

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

You can provide an object, a class or a factory function, more details in the doc: https://docs.nestjs.com/fundamentals/custom-providers

Then in your tests you can mock the methods of the repository this way:

jest.spyOn(repository, 'find').mockResolvedValueOnce([])

It's not the only way to mock, but that's a simple and standard one.