import { TestBed, waitForAsync } from '@angular/core/testing'; import { HttpClientModule } from '@angular/common/http'; import { FormsModule } from '@angular/forms'; import { MockService } from 'ng-mocks'; import { AppComponent } from './app.component'; import { MessagesService } from './messages.service'; import { of } from 'rxjs'; describe('AppComponent', () => { beforeEach( waitForAsync(() => { TestBed.configureTestingModule({ declarations: [AppComponent], imports: [HttpClientModule, FormsModule], providers: [ { provide: MessagesService, useValue: MockService(MessagesService) }, ], }).compileComponents(); }) ); beforeEach(() => { const messageService = TestBed.inject(MessagesService); jest.spyOn(messageService, 'getMessages').mockReturnValue(of([])); }); it('should create the app', () => { const fixture = TestBed.createComponent(AppComponent); const app = fixture.debugElement.componentInstance; expect(app).toBeTruthy(); }); });