Angular2 & TestBed: How to mock AngularFire2/observable data service?

Question

I'm having a really hard time to try to understand how TestBed works and how to use it to mock data retrieval (via AngularFire2 i.e. observables)/pushing in an offline unit test.If someone could provide a simple example to look at it would make things so much easier.

Below is (part of) StateService. I then inject this service in another component and print out the graphModules names, e.g.

graph-modules.component.html

<div *ngFor="let module of s.graphModules$ | async"><div class="module-card">{{module.name}}</div></div>

graph-modules.component.ts

constructor(public s: StateService){}

state.service.ts

@Injectable()
export class StateService {

 graphModules$: FirebaseListObservable<any>;
  private auth;

  constructor(public af: AngularFire) {
    af.auth.subscribe(
      latestAuth => {
        this.graphModules$ = af.database.list('/graphModules', {
          query: {
            orderByChild: 'archived',
            equalTo: false
          }
        });
      },
      errors => {
        this.auth = {uid: 'AUTH PROBLEMS'};
        throw 'Problems authenticating';
      }
    );
  }

  saveToDB(key: string, value: any) { 
     this.af.database.list('/graphModules').update(key, value);
     ...
  }
...
}

What I want like to test is

1) given a mock/stub of "graphModules", the correct number of .card-module will be printed to DOM.

2) after updating one of the modules with s.saveToDB(), the names are updated in the DOM

On a side note, if you have other comments about my "architecture" for data retrieval that'd be most welcome too :)

Many thanks!

EDIT:

Ok, I found out how to fix number 1. The test is passing correctly. Question 2 is yet to be answered. The spec file now looks like this:

graph-modules.component.spec.ts

class MockStateService {
  public graphModules$: Observable<GraphModule[]>;
  constructor () {
    this.graphModules$ = Observable.of<GraphModule[]>([
      {
        name: 'first',
        ...
      },
      {
        name: 'second',
        ...
      }
    ]);
  }
  updateGraphModule(key: string, value: any) {
    // Not sure what to put here in order to emit new value on graphModules$
  }
}



describe('ModulesComponent', () => {
  let fixture:  ComponentFixture<ModulesComponent>;
  beforeEach(() => {
    this.service = new MockStateService();
    TestBed.configureTestingModule({
      imports: [AppModule],
      providers: [{provide: StateService, useValue: this.service }]
    });
    fixture = TestBed.createComponent(ModulesComponent);
  });

  it('should print out two graphModules', async(() => {
    fixture.whenStable().then(() => {
      fixture.detectChanges();
      const test = fixture.nativeElement.querySelectorAll('.module-card');
      expect(fixture.nativeElement.querySelectorAll('.module-card').length).toBe(2);
    });
  }));


  it('should retrieve new data from observer and update DOM when the first graph-module has been given a new name', async(() => {
    fixture.whenStable().then(() => {
      fixture.detectChanges();
      this.service.updateGraphModule(0, {name: 'new name'});
      // What should I write here to test if the DOM is correctly updated?
    });
  }));
 }));
});

Angular2 & TestBed: How to mock AngularFire2/observable data service?

0 Answers0