无法读取null茉莉花角2的属性'injector'

Question

在角度2中运行茉莉花规格时出现此错误：

无法读取null茉莉花角2的属性'injector'

堆栈跟踪：

TypeError: Cannot read property 'injector' of null
    at TestBed._createCompilerAndModule (http://localhost:3002/node_modules/@angular/core/bundles/core-testing.umd.js:834:48)
    at TestBed._initIfNeeded (http://localhost:3002/node_modules/@angular/core/bundles/core-testing.umd.js:800:43)
    at TestBed.createComponent (http://localhost:3002/node_modules/@angular/core/bundles/core-testing.umd.js:884:18)
    at Function.TestBed.createComponent (http://localhost:3002/node_modules/@angular/core/bundles/core-testing.umd.js:714:33)
    at Object.eval (http://localhost:3002/js/app/landing-page/subcomponents/middle-row.component.spec.js:29:49)
    at ZoneDelegate.invoke (http://localhost:3002/node_modules/zone.js/dist/zone.js:232:26)
    at ProxyZoneSpec.onInvoke (http://localhost:3002/node_modules/zone.js/dist/proxy.js:79:39)
    at ZoneDelegate.invoke (http://localhost:3002/node_modules/zone.js/dist/zone.js:231:32)
    at Zone.run (http://localhost:3002/node_modules/zone.js/dist/zone.js:114:43)
    at Object.eval (http://localhost:3002/node_modules/zone.js/dist/jasmine-patch.js:102:34)

我从官方的angular 2测试文档中复制了此规范：

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

describe('BannerComponent', () => {
  beforeEach(() => {
    TestBed.configureTestingModule({
      declarations: [ BannerComponent ], // declare the test component
    });

    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;

  });
});

并对其进行了微调以使其适用于我的代码：

import 'zone.js/dist/long-stack-trace-zone.js';
import 'zone.js/dist/async-test.js';
import 'zone.js/dist/fake-async-test.js';
import 'zone.js/dist/sync-test.js';
import 'zone.js/dist/proxy.js';
import 'zone.js/dist/jasmine-patch.js';

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

import { MiddleRowComponent } from './middle-row.component';

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

describe('MiddleRowComponent', () => {
   beforeEach(() => {
      TestBed.configureTestingModule({
         declarations: [MiddleRowComponent], // declare the test component
      });

      fixture = TestBed.createComponent(MiddleRowComponent);

      comp = fixture.componentInstance; // MiddleRowComponent test instance

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

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

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

为什么会出现错误？没有inject关键字，但我想TestBed可能会在幕后使用它。

Answer 1

在某个时候（执行任何测试之前），您需要通过调用来初始化测试环境TestBed.initTestEnvironment(...)。

您通常会在karma-test-shim文件中看到此操作，如角度快速入门（与测试文档的快速入门相同）所示。但是，如果您不使用此技术，则需要在测试文件中执行此操作。但是initTestEnvironment只能调用一次，因此您还需要在每个测试文件中重置它

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

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