app.component.spec.ts

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

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

describe('AppComponent', () => {
  let de: DebugElement;
  let comp: AppComponent;
  let fixture: ComponentFixture<AppComponent>;

  beforeEach(waitForAsync(() => {
    TestBed.configureTestingModule({declarations: [AppComponent]}).compileComponents();
  }));

  beforeEach(() => {
    fixture = TestBed.createComponent(AppComponent);
    comp = fixture.componentInstance;
    de = fixture.debugElement.query(By.css('h1'));
  });

  it('should create component', () => expect(comp).toBeDefined());

  it('should have expected <h1> text', () => {
    fixture.detectChanges();
    const h1 = de.nativeElement;
    expect(h1.textContent).toMatch(/angular/i, '<h1> should say something about "Angular"');
  });
});