title: Testing redux/react with jest erroring on webworker
body: <p>I'm using React-scripts which includes jest to run tests on my redux model (not using much react yet, still building out the data.</p>
  
  <p>I use a webworker to fetch data via an ajax request. </p>
  
  <p>When I run my tests, <code>Reference Error: Worker is not defined</code>. </p>
  
  <p>I've tried installing a worker npm library and include that as a global in my test.spec file via
   <code>import * as global.Worker from "webworker"</code>, but this doesn't include the webworker in my tests. </p>
  
  <p>I want to avoid having the webworker included in my source, as it isn't needed in the browser, but I would like it for testing, or if I don't test the worker code, at least have my tests not error out because the worker is referenced in the file.</p>