NestJS：拦截器测试中不允许通过字符串文字访问 object

Question

I am testing an Interceptor that requires one service as a dependency. I need to test that a method from this service has been called. The code below is working but since my dependency is private I have to call it like this: service = interceptor['filtersService']; . Typescript doesn't like this and outputs a warning:

object access via string literals is disallowed

Is there another way to spy on a dependency?

describe('CreateClientFilterInterceptor', () => {
  const FiltersServiceMock = jest.fn<Partial<FiltersService>, []>(() => ({
    async create() {
      return (await SubscriberFilterMock) as Filter;
    },
  }));
  let interceptor: CreateClientFilterInterceptor;
  let service;
  beforeAll(async () => {
    interceptor = new CreateClientFilterInterceptor(
      new FiltersServiceMock() as FiltersService,
    );
    service = interceptor['filtersService'];
  });
  it('should call create method from Filter service', async done => {
    spyOn(service, 'create').and.stub();
    (await interceptor.intercept(
      executionContext as ExecutionContext,
      callHandler,
    )).subscribe(() => {
      expect(service.create).toHaveBeenCalled();
      done();
    });
  });
});

Workaround

I did this workaround to get rid of the warning but it doesn't seem right to me.

const serviceName = 'filtersService';
const service = interceptor[serviceName];

Answer 1

Since you are creating the service yourself, you can first create an instance, save it in your service variable and then create the interceptor with it:

service = new FiltersServiceMock() as FiltersService;
interceptor = new CreateClientFilterInterceptor(service);