anchor.diff:  
     But it's not always feasible. For instance, sometimes we need to write tests for existing functionality, like what we're about to do with the rest of Tour of Heroes.
   
  -  但这也并不总是可行的。比如，优势我们需要为现有功能写测试，就像我们即将对《英雄指南》的其余部分所做的那样。
  +  但这也并不总是可行的。比如，有时我们需要为现有功能写测试，就像我们即将对《英雄指南》的其余部分所做的那样。
   
     If we are writing new code though, writing tests might just be what we need to help us track our progress and keep the end result in sight at all times.
   
  
positive.code: 
    We can make our own `my-uppercase` pipe that does exactly the same as the `uppercase` pipe and test that.
  
    我们可以做一个自己的`my-uppercase`管道兵测试它，该管道的功能和`uppercase`管道完全相同。
  
    Since we're getting ready to write some code we want to test, let's take this opportunity to talk just a little bit about [Test Driven Development](https://en.wikipedia.org/wiki/Test-driven_development). There's a lot written about this topic so we don't want to have an exhaustive description here, but rather a practical application.
  
  
negative.code: 
    An Angular pipe is a declarative way in HTML to transform some input into some displayable output.
  
    Angular管道一种以声明的方式，在HTML中把某些输入转换成易于显示的输出。
  
    We don't have a pipe though, since in Tour of Heroes we didn't create any pipes. It uses a pipe though, the `uppercase` pipe that comes with Angular 2.
  
  