anchor.diff:      It works hard to appear useful when in fact it 
       tests the `RouterLinkStubDirective` rather than the _component_.
       This is a common failing of directive stubs.
  +
  +    本例中的“click”测试其实毫无价值。
  +    它显得很有用，但是事实上，它测试的是`RouterLinkStubDirective`，而非测试组件。
  +    这是指令stub的通病。
       
       It has a legitimate purpose in this chapter. 
       It demonstrates how to find a `RouterLink` element, click it, and inspect a result,
  
positive.code:     This is a skill you may need to test a more sophisticated component, one that changes the display,
      re-calculates parameters, or re-arranges navigation options when the user clicks the link.
  
  #why-stubbed-routerlink-tests
  :marked
    ### What good are these tests?
  
    Stubbed `RouterLink` tests can confirm that a component with links and an outlet is setup properly,
    that the component has the links it should have, and that they are all pointing in the expected direction.
    These tests do not concern whether the app will succeed in navigating to the target component when the user clicks a link.
  
    Stubbing the RouterLink and RouterOutlet is the best option for such limited testing goals.
    Relying on the real router would make them brittle.
  
negative.code:   只有selected事件的测试不一样。它确保被选择的`DashboardHeroComponent`英雄确实通过事件绑定被传递到宿主组件。
  
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