小编lau*_*nta的帖子

我正在学习本教程:https://angular.io/guide/testing#component-test-scenarios for karma + jasmine unit testing.这是我的代码:

import { AppComponent } from "./app.component";
import { ComponentFixture, TestBed } from "@angular/core/testing";

describe('AppComponent', () => {

let component: AppComponent;
let fixture:   ComponentFixture<AppComponent>;
let h1:        HTMLElement;

beforeEach(() => {
  TestBed.configureTestingModule({
    declarations: [ AppComponent ],
  });
  fixture = TestBed.createComponent(AppComponent);
  component = fixture.componentInstance; 
  h1 = fixture.nativeElement.querySelector('h1');
});

it('should display original title', () => {
    expect(h1.textContent).toContain("Ciao");
  });

});

当我运行测试时,我得到以下异常:

 TypeError: Cannot read property 'getComponentFromError' of null
    at TestBed._initIfNeeded (D:/Users/apwzp/AppData/Local/Temp/karma-typescript-bundle-11944DDd01l2f5Y0P.js:1020:52)
    at TestBed.createComponent (D:/Users/apwzp/AppData/Local/Temp/karma-typescript-bundle-11944DDd01l2f5Y0P.js:1174:14)
    at …