title: Temporarily get jest coverage to show only files in a specific folder
body: <p>For my reactjs app, I'm adding integration tests to a view and want to keep an eye on coverage along the way.  I'm currently getting all files on every run.</p>
  <h2>Question</h2>
  <p>While adding tests to increase coverage, how can I get jest coverage to show only files in a specific folder?</p>
  <h2>Examples tried</h2>
  <ul>
  <li><p>$ <code>yarn test --collectCoverageFrom=src/app/components/Tools</code>
  Test run, bu no coverage is showing here.</p>
  </li>
  <li><p>$ <code>yarn test Tools --coverage --collectCoverageFrom=src/app/components/Tools</code>
  I get <code>Ran all test suites matching &quot;Tools&quot;.</code></p>
  </li>
  <li><p>$ <code>yarn test src/app/components/Tools --coverage</code><br />
  Here I see the coverage percentage is smaller but still lists all files.</p>
  </li>
  <li><p>$ <code>yarn test -o --coverage</code>
  Again as the previous, I see the coverage percentage is smaller but still lists all files.</p>
  </li>
  </ul>