anchor.diff:  :marked
     Notice that `TestBed.configureTestingModule` no longer provides a (fake) `HeroService` because it's [not needed](#stub-hero-detail-service).
   
  -  注意，`TestBed.configureTestingModule`不再提供一个（伪造）`HeroService`，因为它是[没必要的](#stub-hero-detail-service)
  +  注意，`TestBed.configureTestingModule`不再提供一个（伪造）`HeroService`，因为它是[没必要的](#stub-hero-detail-service)。
   
   #override-component-method
   :marked
     ### The _overrideComponent_ method
   
  +  ### **overrideComponent**方法
  +
     Focus on the `overrideComponent` method.
  +
  +  注意这个`overrideComponent`方法。
   +makeExample('testing/ts/app/hero/hero-detail.component.spec.ts', 'override-component-method', 'app/hero/hero-detail.component.spec.ts (overrideComponent)')(format='.')
   :marked
     It takes two arguments: the component type to override (`HeroDetailComponent`) and an override metadata object.
     The [overide metadata object](#metadata-override-object) is a generic defined as follows:
  +
  +  它接受两个参数：要替换的组件类型(`HeroDetailComponent`)和一个用于替换的元数据对象。
  +  [替换元数据对象](#metadata-override-object)是一个泛型类，就像这样：
   
   code-example(format="." language="javascript").
     type MetadataOverride<T> = {
  
positive.code:   A metadata override object can either add-and-remove elements in metadata properties or completely reset those properties.
    This example resets the component's `providers` metadata.
  
    The type parameter, `T`,  is the kind of metadata you'd pass to the `@Component` decorator:
  code-example(format="." language="javascript").
      selector?: string;
      template?: string;
  
negative.code: :marked
    ### _StubHeroDetailService_
  
    ### _StubHeroDetailService_
  
    This example completely replaces the component's `providers` with an array containing the `StubHeroDetailService`.
    The `StubHeroDetailService` is dead simple. It doesn't need a `HeroService` (fake or otherwise).
  
    本例彻底替换组件的`providers`为包含`StubHeroDetailService`的数组。
    `StubHeroDetailService`非常简单。它不需要`HeroService`(假不假不重要)
  +makeExample('testing/ts/app/hero/hero-detail.component.spec.ts', 'stub-hds', 'app/hero/hero-detail.component.spec.ts (StubHeroDetailService)')(format='.')
  :marked
    ### The override tests
  
    ### 替换的测试
  
    Now the tests can control the component's hero directly by manipulating the stub's `testHero`.
  
    现在，测试可以通过操控stub的`testHero`，直接控制组件的英雄。
  
  +makeExample('testing/ts/app/hero/hero-detail.component.spec.ts', 'override-tests', 'app/hero/hero-detail.component.spec.ts (override tests)')(format='.')
  :marked
    ### More overrides
  
    ### 更多替换
    
    The `TestBed.overrideComponent` method can be called multiple times for the same or different components.
    The `TestBed` offers similar `overrideDirective`, `overrideModule`, and `overridePipe` methods
    for digging into and replacing parts of these other classes.
  