anchor.diff:          which application and test files to load, which browser(s) to use,
           and how to report test results.
   
  +        Karma配置文件。它指定使用哪些插件、加载哪个应用和测试文件、使用哪些浏览器和如何报告测试结果。
  +
           It loads three other setup files:
  +
  +        它加载三种配置文件：
  +
           * `systemjs.config.js` 
           * `systemjs.config.extras.js`
           * `karma-test-shim.js`
  
positive.code:         This shim prepares karma specifically for the Angular test environment 
          and launches karma itself. 
          It loads the `systemjs.config.js` file as part of that process.
    tr
      td(style="vertical-align: top") <code>systemjs.config.js</code>
      td
  
negative.code:         loads the application and test modules.
          This script tells SystemJS where to find the module files and how to load them.
          It's the same version of the file used by QuickStart-based applications.
  
          [SystemJS](https://github.com/systemjs/systemjs/blob/master/README.md) 
          加载应用和测试模块。本脚本告诉SystemJS去哪儿寻找模块文件，以及如何加载它们。
          它的文件版本和基于《快速起步》的应用使用的一样。
    tr
      td(style="vertical-align: top") <code>systemjs.config.extras.js</code>
      td
  