Unit testing with private service injected using j

Question

I have a problem trying to unit test an angular service. I want to verify that this service is properly calling another service that is injected into it.

Lets say I have this ServiceToTest that injects ServiceInjected:

ServiceToTest .service.ts

@Injectable()
export class ServiceToTest  {
    constructor(private _si: ServiceInjected) {}
    public init() {
      this._si.configure();
    }

}

ServiceInjected.service.ts

@Injectable()
export class ServiceInjected {
    constructor() {}
    public configure() {
    /*Some actions*/
    }

}

With these services, now I write my unit test:

const serviceInjectedStub = {
  configure(): void {}
}


describe('ServiceToTest service Test', () => {
  beforeEach(() => {
    TestBed.configureTestingModule({
      providers: [ServiceToTest ,
        { provide: ServiceInjected, useValue: serviceInjectedStub }]
    });
  });
  
  it('should be initialize the service injected', inject([ServiceToTest],
    (tService: ServiceToTest) => {
      spyOn(serviceInjectedStub, 'configure');
      tService.init();
      expect(serviceInjectedStub.configure).toHaveBeenCalled();
    }));

I expected my test to be positive, however I receive the following error:

Expected spy configure to have been called.

On the other hand, it works OK if I set the injected service public in this way:

private _si: ServiceInjected by public si: ServiceInjected

Answer 1

Use this:

spyOn(serviceInjectedStub, 'configure').and.returnValue(config); // config is a mock

Answer 2

You don't spy on the service tied to your TestBed. Get the service from your Testbed

beforeEach(() => {
  TestBed.configureTestingModule({
    providers: [ServiceToTest ,
      { provide: ServiceInjected, useValue: serviceInjectedStub }]
  });
  injectedService = TestBed.get(ServiceInjected);
});

And test on it

spyOn(injectedService, 'configure').and.returnValue(/* return same data type here */);
// ...
expect(injectedService.configure).toHaveBeenCalled();

Answer 3

Or you can use jasmine.createSpyObj and provide it with useValue like bellow:

describe('YourComponent', () => {

  let serviceInjectedSpy: jasmine.SpyObj<ServiceInjected>;

  beforeEach(async(() => {

     // notice here
     serviceInjectedSpy = jasmine.createSpyObj('ServiceInjected', ['configure']);

     TestBed.configureTestingModule({
        declarations: [YourComponent],
        providers: [
           {provide: ServiceInjected, useValue: serviceInjectedSpy}
        ],
        imports: [
         ...
        ]
     }).compileComponents().then(() => {
        fixture = TestBed.createComponent(YourComponent);
        component = fixture.componentInstance;
     });
  });

  it('should assert my test', () => {
       serviceInjectedSpy.configure.and.returnValue(/* what you want */);
       component.init();
       expect(serviceInjectedSpy.configure).toHaveBeenCalled();
  });

});

Answer 4

You should use a mock service like:

class MockAuthService extends AuthService {
  isAuthenticated() {
    return 'Mocked';
  }
}

In this way you have control over the service that you are not testing and focus on the other.

Now, to check if the service is being called correctly maybe you can add a mock variable that is turned to true whenever the mock service is called.