Testing

Unit testing

Since the ClsService and any created Proxy providers are just another injectable providers, they can be entirely mocked out in unit tests using standard techniques.

E2E testing

In E2E tests, you should use the real ClsService implementation to test the entire application in a real-world scenario. Unless you're using any plugins that require special handling, you should not need to do anything special to set up E2E tests.

Integration testing

In certain integration tests involving flows that span multiple modules but not the entire application, you might still want to use the real ClsService implementation for context propagation.

In that case, you will need to wrap the context-aware piece of code with a call to ClsService#run or ClsService#runWith.

Example

cat.service.ts

@Injectable()
export class CatService {
    constructor(
        private readonly cls: ClsService,
        private readonly catRepository: CatRepository,
    ) {}

    getCatForUser() {
        const userId = this.cls.get('userId');
        return this.catRepository.getForUser(userId);
    }
}

cat.service.spec.ts

describe('CatService', () => {
  let service: CatService
  let cls: ClsService
  const mockCatRepository = createMock<CatRepository>()

  beforeEach(async () => {
    const module = await Test.createTestingModule({
      // Set up most of the testing module as we normally would.
      providers: [
        CatService,
        {
          provide: CatRepository
          useValue: mockCatRepository
        }
      ],
      imports: [
        // Import the static version of ClsModule which only provides
        // the ClsService, but does not set up any enhancers
        // that would automatically set up the context on request.
        ClsModule
      ],
    }).compile()

    service = module.get(CatService)

    // Also retrieve the ClsService for later use.
    cls = module.get(ClsService)
  })

  describe('getCatForUser', () => {
    it('retrieves cat based on user id', async () => {
      const expectedUserId = 42
      mockCatRepository.getForUser.mockImplementationOnce(
        (id) => ({ userId: id })
      )

      // Wrap the test call in the `runWith` method
      // in which we can pass hand-crafted store values.
      const cat = await cls.runWith(
        // populate the store with mocked values for the test
        { userId: expectedUserId },
        () => service.getCatForUser()
      )

      expect(cat.userId).toEqual(expectedUserId)
    })
  })
})