app.component.spec.ts

import {async, TestBed} from '@angular/core/testing';

import {AppComponent} from './app.component';

describe('AppComponent', () => {
  beforeEach(async(() => {
    TestBed
        .configureTestingModule({
          declarations: [AppComponent],
        })
        .compileComponents();
  }));
  it('should create the app', async(() => {
       const fixture = TestBed.createComponent(AppComponent);
       const app = fixture.debugElement.componentInstance;
       expect(app).toBeTruthy();
     }));
  it(`should have as title 'app'`, async(() => {
       const fixture = TestBed.createComponent(AppComponent);
       const app = fixture.debugElement.componentInstance;
       expect(app.title).toEqual('app');
     }));
  it('should render title in a h1 tag', async(() => {
       const fixture = TestBed.createComponent(AppComponent);
       fixture.detectChanges();
       const compiled = fixture.debugElement.nativeElement;
       expect(compiled.querySelector('h1').textContent)
           .toContain('Welcome to app!');
     }));
});