anchor.diff:    The `WelcomeComponent` displays a welcome message to the logged in user.
     It knows who the user is based on a property of the injected `UserService`:
   
  -  组件经常有服务依赖。`WelcomeComponent`为登陆的用户显示一条欢迎信息。它从注入的`UserService`的属性知道用户的身份：
  +  组件经常有服务依赖。`WelcomeComponent`为登陆的用户显示一条欢迎信息。它从注入的`UserService`的属性得知用户的身份：
     
   +makeExample('testing/ts/app/welcome.component.ts', '', 'app/welcome.component.ts')(format='.')
   :marked
  
positive.code:   
    `TestBed.createComponent` creates an instance of `BannerComponent` to test and returns a [fixture](#component-fixture).
  
    `TestBed.createComponent`创建`BannerComponent`组件的实例用来测试和返回[fixture](#component-fixture)。
  
    `TestBed.createComponent` closes the current `TestBed` instance to further configuration.
    You cannot call any more `TestBed` configuration methods, not `configureTestModule` 
  
negative.code:   it's perfect for a first encounter with the `TestBed`.
  
    `BannerComponent`有内联模板和插值表达式绑定。
    在真实应用场景中，这个组件可能过于简单，不值得测试。但是我们是第一次接触`TestBed`，所以用它非常合适。
  
    The corresponding `app/banner-component.spec.ts` sits in the same folder as the component,
    for reasons explained [here](#q-spec-file-location);
  
    对应的`app/banner-component.spec.ts`在与组件相同的目录，参见[这里](#q-spec-file-location)的解释。
  
    Start with ES6 import statements to get access to symbols referenced in the spec.
  
  