title: Files containing only exports decreases the test coverage Jest
body: <p>I'm using create-react-app which uses Jest for testing.
  I have <code>index.js</code> files containing exports lines like </p>
  
  <pre><code>export { default } from './App.component';
  </code></pre>
  
  <p>which decreases the test coverage of my application.</p>
  
  <p><strong>Q:</strong>
  How to test such files or at least ignore them?</p>