title: yarn test - Network request failed
body: <p>created a react project using create-react-app however when  I go to run <code>yarn test</code> to see if the initial tests pass I get</p>
  
  <pre><code>/home/afenwick/Development/road-to-react-learning/node_modules/react-scripts/scripts/test.js:22
  throw err;
  ^
  TypeError: Network request failed`
  error Command failed with exit code 1.  
  </code></pre>
  
  <p>If I set up a brand new app it works totally fine, have not made any changes to App.test.js, just trying to run the default test. <code>yarn start</code> works fine, spins up my app in the browser.<br>
  Have tried deleting <code>node_modules</code><br>
  Also tried <code>npm install</code> instead and <code>npm run tests</code> but that doesnt install my dependencies and then also errors the tests.<br>
  OS: Antergos Linux<br>
  Github repo: <a href="https://github.com/Fenwick17/road-to-react-learning" rel="nofollow noreferrer">https://github.com/Fenwick17/road-to-react-learning</a><br>
  Stepped through my commits to locate the issue, and appears to be caused in <a href="https://github.com/Fenwick17/road-to-react-learning/commit/4b6069181a39861e531b550ebb8689695db042bb" rel="nofollow noreferrer">https://github.com/Fenwick17/road-to-react-learning/commit/4b6069181a39861e531b550ebb8689695db042bb</a> so I will work through the changes to rectify.</p>