Karma + Jasmine: Cannot read property 'getComponentFromError'

问题

I am following this tutorial: https://angular.io/guide/testing#component-test-scenarios for karma+jasmine unit testing. Here my code:

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");
  });

});

When I run the test I get the following exception:

 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 Function.TestBed.createComponent (D:/Users/apwzp/AppData/Local/Temp/karma-typescript-bundle-11944DDd01l2f5Y0P.js:876:29)
    at UserContext.<anonymous> (assets/app/app.component.spec.ts:14:20 <- assets/app/app.component.spec.js:13:37)
    at ZoneDelegate.invoke (node_modules/zone.js/dist/zone.js:388:26)
    at ProxyZoneSpec.onInvoke (node_modules/zone.js/dist/proxy.js:79:39)
    at ZoneDelegate.invoke (node_modules/zone.js/dist/zone.js:387:32)
    at Zone.run (node_modules/zone.js/dist/zone.js:138:43)
    at UserContext.<anonymous> (node_modules/zone.js/dist/jasmine-patch.js:106:34)

Does anyone know how to solve it?

回答1:

I ran into something similar and found the answer here: Cannot read property 'injector' of null jasmine angular 2.

I just added this to my beforeEach() method which solved this error for me (there were a few others I had to overcome before I got this all working entirely).

 TestBed.resetTestEnvironment();
 TestBed.initTestEnvironment(BrowserDynamicTestingModule,
    platformBrowserDynamicTesting());

Basically it was just a matter of changing this:

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

import { BrowserDynamicTestingModule,
platformBrowserDynamicTesting } from '@angular/platform-browser-dynamic/testing';

beforeEach(() => {
 TestBed.resetTestEnvironment();
 TestBed.initTestEnvironment(BrowserDynamicTestingModule,
    platformBrowserDynamicTesting());

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

来源：https://stackoverflow.com/questions/49068013/karma-jasmine-cannot-read-property-getcomponentfromerror

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angular

unit-testing

jasmine

karma-runner

zone.js