anchor.diff:    Each overide method takes a `MetadataOverride<T>` where `T` is the kind of metadata
     appropriate to the method, the parameter of an `@NgModule`, `@Component`, `@Directive`, or `@Pipe`.
   
  -
  +  每一个重载方法接受一个`MetadataOverride<T>`，这里`T`是适合这个方法的元数据类型，也就是`@NgModule`、`@Component`、`@Directive`或者`@Pipe`的参数。
   
   code-example(format="." language="javascript").
     type MetadataOverride<T> = {
  
positive.code:         or `styleUrls` because fetching component template and style files is necessarily asynchronous.
          See [above](#compile-components).
  
          Once called, the `TestBed` configuration is frozen for the duration of the current spec.
  
    tr
      td(style="vertical-align: top") <code>createComponent<T></code>
  
negative.code:         Replace metadata for the given `NgModule`. Recall that modules can import other modules.
          The `overrideModule` method can reach deeply into the current testing module to
          modify one of these inner modules.
  
          替换指定的`NgModule`的元数据。回想一下，模块可以导入其他模块。
          `overrideModule`方法可以深入到当前测试模块深处，修改其中一个内部模块。
    tr
      td(style="vertical-align: top") <code>overrideComponent</code>
      td
        :marked
          Replace metadata for the given component class which could be nested deeply 
          within an inner module.
  
          替换指定组件类的元数据，该组件类可能嵌套在一个很深的内部模块中。
    tr
      td(style="vertical-align: top") <code>overrideDirective</code>
      td
        :marked
          Replace metadata for the given directive class which could be nested deeply 
          within an inner module.
  
          替换指定的指令类的元数据，该指令可能嵌套在一个很深的内部模块中。
    tr
      td(style="vertical-align: top") <code>overridePipe</code>
      td
        :marked
          Replace metadata for the given pipe class which could be nested deeply 
          within an inner module.
          
          替换指定的管道类的元数据，该管道可能嵌套在一个很深的内部模块中。      
    tr
      td(style="vertical-align: top").
        <a id="testbed-get"></a>
  