Karma + Jasmine：无法阅读属性 'getComponentFromError'

Question

我正在学习本教程：https://angular.io/guide/testing#component-test-scenarios 用于 karma+jasmine 单元测试。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 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)

有人知道怎么解决吗？

Answer 1

我运行找到了类似的东西并在这里找到了答案：。

我刚刚将它添加到我的 beforeEach() 方法中，它为我解决了这个错误（在我完全正常工作之前，我还必须克服其他一些问题）。

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

基本上这只是一个改变这个的问题：

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

到

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');
});

Answer 2

如果您要升级到 jest-preset-angular 版本 >= 9，将 import 'jest-preset-angular'; 替换为 import 'jest-preset-angular/setup-jest'; 似乎可以解决问题，而无需添加 beforeAll每次测试。

见https://github.com/thymikee/jest-preset-angular/blob/a4251dd9776fe4d99af828b43acc3ea3a1bb5f90/CHANGELOG.md#breaking-changes

Answer 3

只需将此添加到根文件夹中的 setupJest.ts：

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

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

然后将其添加到 jest 配置中：

"setupFilesAfterEnv": [
  "<rootDir>/setupJest.ts"
],

Karma + Jasmine：无法阅读属性 'getComponentFromError'

Karma + Jasmine: Cannot read property 'getComponentFromError'

unit-testing

jasmine

karma-runner

zone.js

angular

Karma + Jasmine：无法阅读 属性 'getComponentFromError'

Karma + Jasmine: Cannot read property 'getComponentFromError'

unit-testing

jasmine

karma-runner

zone.js

angular

Karma + Jasmine：无法阅读属性 'getComponentFromError'