NullInjectorError:在Angular 2中进行测试时,StaticInjectorError(DynamicTestModule)

时间:2019-03-01 20:41:54

标签: javascript angular unit-testing frontend angular2-services

我是Angular2的新手,正在尝试在app.component.spec.ts文件中编写测试。我的应用程序相对简单,除了它从第三方库(由同事编写)导入LoginComponent和LogoutComponent之外。这些组件现在分别用于路由登录或注销,非常简单。运行ng serve编译正常,应用程序“顺利”运行。但是,运行ng test会给我这个错误:

NullInjectorError: StaticInjectorError(DynamicTestModule)[LogoutComponent -> SessionService]: 
  StaticInjectorError(Platform: core)[LogoutComponent -> SessionService]: 
    NullInjectorError: No provider for SessionService!

LogoutComponent是从其他项目导入的。这个错误是否意味着我需要进入该项目并进行一些更改,还是应该在我的项目中以某种方式嘲笑SessionService?

规范代码:

import {} from 'jasmine';
import {async, TestBed} from '@angular/core/testing';
import {RouterTestingModule} from '@angular/router/testing';
import {AuthErrorStateService, LogoutComponent} from '@custom-library';

import {AppComponent} from './app.component';
import {AppErrorStateService} from './core/error-states/app-error-state.service';
import {TopNavComponent} from './core/top-nav/top-nav.component';

describe('AppComponent', () => {
  beforeEach(async(() => {
    TestBed
        .configureTestingModule({
          imports: [RouterTestingModule],
          providers: [
            AppErrorStateService, AuthErrorStateService
          ],
          declarations: [AppComponent, TopNavComponent, LogoutComponent],
        })
        .compileComponents();
  }));

  it('should create the app', () => {
    const fixture = TestBed.createComponent(AppComponent);
    const app = fixture.debugElement.componentInstance;
    expect(app).toBeTruthy();
  });

  it(`should have as title 'My App'`, () => {
    const fixture = TestBed.createComponent(AppComponent);
    const app = fixture.debugElement.componentInstance;
    expect(app.title).toEqual('My App');
  });

  it('should render title in a h1 tag', () => {
    const fixture = TestBed.createComponent(AppComponent);
    fixture.detectChanges();
    const compiled = fixture.debugElement.nativeElement;
    expect(compiled.querySelector('h1').textContent).toEqual('Welcome to My App!');
  });
});

1 个答案:

答案 0 :(得分:1)

问题在于像这样声明TestBed中的多个组件

 declarations: [AppComponent, TopNavComponent, LogoutComponent]

导致测试调用compileComponents()时实例化多个组件。发生这种情况时,declarations数组中的每个组件都需要在providers数组中声明其依赖项才能完成实例化。已声明的组件之一取决于SessionService,但是提供程序中不存在该服务,因此您获得了NullInjectorError

有两种解决方法:

  • 仅在declarations数组中声明一个组件并添加 schemas: [ CUSTOM_ELEMENTS_SCHEMA ]TestBed配置 对象
  • 继续声明多个组件并添加所有 每个组件的依赖项(或其模拟) providers数组