Mocking & E2E Tests — Series 2

Preview — 3 of 10 questions

What does this accomplish?

javascript

const moduleRef = await Test.createTestingModule({ imports: [AppModule] })
  .overrideGuard(JwtAuthGuard)
  .useValue({ canActivate: (ctx: ExecutionContext) => {
    ctx.switchToHttp().getRequest().user = { id: 'u_1', roles: ['admin'] };
    return true;
  }})
  .compile();

AIt disables all guards in the application, including globally registered ones

BIt replaces that specific guard wherever it is bound, so the endpoint tests exercise the handler's behaviour with a known user instead of going through a real login on every request

CIt removes the guard's metadata, so the route becomes public

DIt only affects guards bound with @UseGuards(), not those registered through APP_GUARD

Why did validation not run?

javascript

app = moduleRef.createNestApplication();
await app.init();

const res = await request(app.getHttpServer()).post('/cats').send({ name: 123 });
// expected 400, received 201

AcreateNestApplication() disables validation deliberately, to keep tests fast

Bsupertest bypasses the enhancer pipeline and calls handlers directly

CThe DTO must be re-registered on the testing module for its decorators to apply

DGlobal pipes registered in main.ts with app.useGlobalPipes(...) are not part of the module graph, so a test that builds its own application never applies them — either register them in the test too, or move the registration into a module as an APP_PIPE provider so it travels with the graph

Why is getRepositoryToken(Cat) needed?

javascript

const moduleRef = await Test.createTestingModule({
  providers: [
    CatsService,
    { provide: getRepositoryToken(Cat), useValue: { findOneBy: jest.fn(), save: jest.fn() } },
  ],
}).compile();

A@InjectRepository(Cat) injects under a generated token derived from the entity, not under the Repository class — so the override must use the same token, which this helper computes

BIt converts the mock object into a real Repository instance

CIt registers the entity with the test's data source

DIt is optional; providing Repository directly works identically

Answer all 10 questions (7 more), see explanations for every answer, and track your score.