NestJS/TypeORM unit testing: Can't resolve dependencies of JwtService

Question

I'm trying to unit test this controller and mock away the services/repositories that it needs.

@Controller('auth')
export class AuthController {
    constructor(
        private readonly authService: AuthService,
        private readonly usersService: UsersService,
    ) {}

    @Post('register')
    public async registerAsync(@Body() createUserModel: CreateUserModel) {
        const result = await this.authenticationService.registerUserAsync(createUserModel);

        // more code here
    }

    @Post('login')
    public async loginAsync(@Body() login: LoginModel): Promise<{ accessToken: string }> {
        const user = await this.usersService.getUserByUsernameAsync(login.username);

        // more code here
    }
}

Here is my unit test file:

describe('AuthController', () => {
    let authController: AuthController;
    let authService: AuthService;

    beforeEach(async () => {
        const moduleRef: TestingModule = await Test.createTestingModule({
            imports: [JwtModule],
            controllers: [AuthController],
            providers: [
                AuthService,
                UsersService,
                {
                    provide: getRepositoryToken(User),
                    useClass: Repository,
                },
            ],
        }).compile();

        authController = moduleRef.get<AuthenticationController>(AuthenticationController);
        authService = moduleRef.get<AuthenticationService>(AuthenticationService);
    });

    describe('registerAsync', () => {
        it('Returns registration status when user registration succeeds', async () => {
            let createUserModel: CreateUserModel = {...}

            let registrationStatus: RegistrationStatus = {
                success: true,
                message: 'User registered successfully',
            };

            jest.spyOn(authService, 'registerUserAsync').mockImplementation(() =>
                Promise.resolve(registrationStatus),
            );

            expect(await authController.registerAsync(createUserModel)).toEqual(registrationStatus);
        });
    });
});

But when running this, I get the following error(s):

  ● AuthController › registerAsync › Returns registration status when user registration succeeds

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

    Potential solutions:
    - If JWT_MODULE_OPTIONS is a provider, is it part of the current JwtModule?
    - If JWT_MODULE_OPTIONS is exported from a separate @Module, is that module imported within JwtModule?
      @Module({
        imports: [ /* the Module containing JWT_MODULE_OPTIONS */ ]
      })

      at Injector.lookupComponentInParentModules (../node_modules/@nestjs/core/injector/injector.js:191:19)
      at Injector.resolveComponentInstance (../node_modules/@nestjs/core/injector/injector.js:147:33)
      at resolveParam (../node_modules/@nestjs/core/injector/injector.js:101:38)
          at async Promise.all (index 0)
      at Injector.resolveConstructorParams (../node_modules/@nestjs/core/injector/injector.js:116:27)
      at Injector.loadInstance (../node_modules/@nestjs/core/injector/injector.js:80:9)
      at Injector.loadProvider (../node_modules/@nestjs/core/injector/injector.js:37:9)
      at Injector.lookupComponentInImports (../node_modules/@nestjs/core/injector/injector.js:223:17)
      at Injector.lookupComponentInParentModules (../node_modules/@nestjs/core/injector/injector.js:189:33)

  ● AuthController › registerAsync › Returns registration status when user registration succeeds

    Cannot spyOn on a primitive value; undefined given

      48 |             };
      49 |
    > 50 |             jest.spyOn(authService, 'registerUserAsync').mockImplementation(() =>
         |                  ^
      51 |                 Promise.resolve(registrationStatus),
      52 |             );
      53 |

      at ModuleMockerClass.spyOn (../node_modules/jest-mock/build/index.js:780:13)
      at Object.<anonymous> (Authentication/authentication.controller.spec.ts:50:18)

I'm not quite sure how to proceed so I'd like some help.

Answer 1

There's a few things I'm noticing here:

1. if you're testing the controller, you shouldn't need to mock more than one level deep pf services

2. you should almost never have a use case where you need an imports array in a unit test.

What you can do for your test case instead is something similar to the following:

beforeEach(async () => {
  const modRef = await Test.createTestingModule({
    controllers: [AuthController],
    providers: [
      {
        provide: AuthService,
        useValue: {
          registerUserAsync: jest.fn(),
        }

      },
      {
        provide: UserService,
        useValue: {
          getUserByUsernameAsync: jest.fn(),
        }
      }
    ]
  }).compile();
});

Now you can get the auth service and user service using modRef.get() and save them to a variable to add mocks to them later. You can check out this testing repository which has a lot of other examples.