title: Why tsconfig.spec.json is using CommonJs in Angular Cli?
body: <p>I was just checking the files generated by angular cli. I noticed that tsconfig.spec.json is using commonJs as module, and tsconfig.app.json is using es2015 as module.</p>
  
  <p>Is there any reason for choosing different module implementations?</p>
  
  <p>Angular CLI version: 1.1.1</p>