title: React document.createRange is not a function
body: <p>I'm using Enzyme with Jest in Create-react-app application.</p>
  
  <p>Current behavior
  I have a test which uses the mount method for a React component to find an element on a page. The test passes but a warning gets printed out:</p>
  
  <p>(node:79591) UnhandledPromiseRejectionWarning: TypeError: document.createRange is not a function</p>
  
  <p>The test in question:</p>
  
  <pre><code>import React from "react";
  import { shallow, mount } from "enzyme";
  import UnitGroup from './UnitGroup';
  import { UnitGroupHeading } from '../UnitGroupHeading/UnitGroupHeading';
  
  it('should render properly', () =&gt; {
     shallow(&lt;UnitGroup /&gt;);
  });
  
  it('should render UnitGroupHeading properly', () =&gt; {
    const wrapper = mount(&lt;UnitGroup unit={{name: 'test'}} /&gt;);
    expect(wrapper.find(UnitGroupHeading)).toHaveLength(1);
  });
  </code></pre>