angular-docs-cn/public/docs/_examples/testing/ts/app/banner.component.spec.ts

// #docplaster
import { async, ComponentFixture, TestBed } from '@angular/core/testing';
import { By }              from '@angular/platform-browser';
import { DebugElement }    from '@angular/core';

import { BannerComponent } from './banner.component';

describe('BannerComponent (templateUrl)', () => {

  let comp:    BannerComponent;
  let fixture: ComponentFixture<BannerComponent>;
  let de:      DebugElement;
  let el:      HTMLElement;

  // #docregion async-before-each
  // async beforeEach
  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [ BannerComponent ], // declare the test component
    })
    .compileComponents();  // compile template and css
  }));
  // #enddocregion async-before-each

  // #docregion sync-before-each
  // synchronous beforeEach
  beforeEach(() => {
    fixture = TestBed.createComponent(BannerComponent);

    comp = fixture.componentInstance; // BannerComponent test instance

    // query for the title <h1> by CSS element selector
    de = fixture.debugElement.query(By.css('h1'));
    el = de.nativeElement;
  });
  // #enddocregion sync-before-each

  it('no title in the DOM until manually call `detectChanges`', () => {
    expect(el.textContent).toEqual('');
  });

  it('should display original title', () => {
    fixture.detectChanges();
    expect(el.textContent).toContain(comp.title);
  });

  it('should display a different test title', () => {
    comp.title = 'Test Title';
    fixture.detectChanges();
    expect(el.textContent).toContain('Test Title');
  });

});