title: Cannot mock react-native-sound with Jest
body: <p>When I try to mock <a href="https://github.com/zmxv/react-native-sound" rel="nofollow noreferrer">react-native-sound</a> with Jest I get the following error:</p>
  
  <pre class="lang-js prettyprint-override"><code>//PlayerService.js
  import Sound from 'react-native-sound';
  
  try {
    console.log('Sound: ' + JSON.stringify(Sound)); //Sound: {}
    _trackPlaying = new Sound('path', Sound.LIBRARY, error =&gt; { });
  } catch (error) {
    console.log('error: ' + JSON.stringify(error)); //error: {}
  }
  </code></pre>
  
  <pre class="lang-js prettyprint-override"><code>//PlayerService.tests.js
  jest.mock('react-native-sound', () =&gt; ({
    Sound: jest.fn((path, type, callback) =&gt; {
  
    })
  }));
  </code></pre>
  
  <p>// package.json</p>
  
  <pre><code>{
    "devDependencies": {
      "babel-cli": "^6.26.0",
      "babel-jest": "^21.2.0",
      "babel-plugin-transform-flow-strip-types": "^6.22.0",
      "babel-preset-es2015": "^6.24.1",
      "babel-preset-flow": "^6.23.0",
      "flow": "^0.2.3",
      "jest": "^21.2.1"
    },
    "jest": {
      "modulePathIgnorePatterns": [
        "__mocks__/"
      ]
    },
    "dependencies": {
      "react-native-sound": "^0.10.4"
    }
  }
  </code></pre>
  
  <p>Alternatively I've tried setting up a manual mock in a separated file (<code>__mock__</code> folder) with similar luck:</p>
  
  <pre class="lang-js prettyprint-override"><code>//__mocks__/react-native-sound.js
  const Sound = jest.genMockFromModule('react-native-sound');
  
  Sound = (path, type, callback) =&gt; {
    console.log("mocked");
  }
  
  module.exports = Sound;
  
  //__tests__/PlayerService.tests.js
  jest.mock('react-native-sound'); // doesn't work
  </code></pre>
  
  <p>Any guidance or advice will be greatly appreciated. Thanks much in advance!</p>