title: Jest + ES2015 import
body: <p>I am making an exercise with ES2015, Jest, React and I get this error:</p>
  
  <pre><code>TypeError: Property description must be an object: undefined
  at defineProperties (native)
  at Object.eval (&lt;PROJECT&gt;/node_modules/event-emitter/index.js:127:8)
  </code></pre>
  
  <p>After digging into it, I think it is related to the import of the nodeModule EventEmitter or by extending the class by it.</p>
  
  <p>This is the code of the script file:</p>
  
  <pre><code>import EventEmitter from 'event-emitter';
  import AppDispatcher from '../dispatcher/app-dispatcher';
  
  import {
      ACTION_CURSOR_POSITION_CHANGED,
      ACTION_IS_DRAGGING_CHANGED
  } from '../constants/actions';
  
  let _draggingStoreInstance = null;
  
  /**
   * DraggingStore class
   */
  export default class DraggingStore extends EventEmitter
  {
      /**
       * Constructor
       */
      constructor () {
      // ...
  </code></pre>
  
  <p>The source code of the test file looks like this:</p>
  
  <pre><code>import '../unmock/dragging-store.unmock.js';
  import DraggingStore from '../../src/stores/dragging-store';
  
  describe('Dragging Store', () =&gt; {
     let draggingStoreInstance = null;
  
     beforeEach(() =&gt; {
         draggingStoreInstance = DraggingStore.getInstance();
     });
  
     it('should be defined', () =&gt; {
         expect(DraggingStore).toBeDefined();
         expect(draggingStoreInstance).toBeDefined();
     });
  });
  </code></pre>
  
  <p>I made an extra file for excluding mocks:</p>
  
  <pre><code>jest.dontMock('../../src/stores/dragging-store.js');
  jest.dontMock('../../src/dispatcher/app-dispatcher.js');
  jest.dontMock('../../src/constants/actions.js');
  </code></pre>
  
  <p>The code itself runs smoothly in the browser after compiling, but the test engine gives the error.</p>
  
  <p>I added this in my package.json:</p>
  
  <pre><code>"scripts": {
      "test": "jest"
    },
   "jest": {
      "scriptPreprocessor": "./node_modules/babel-jest",
      "unmockedModulePathPatterns": [
        "./node_modules/react"
      ],
      "collectCoverage": true,
      "testDirectoryName": "spec",
      "moduleFileExtensions": [
        "js"
      ],
      "collectCoverageOnlyFrom": {
          // All files to test
      }
    }
  </code></pre>
  
  <p>Does anyone have a clue how to get around the problem?
  Thanks in advance...</p>
  
  <p>Update: full source code can be found here: <a href="https://github.com/dejakob/unlease-chess" rel="nofollow">https://github.com/dejakob/unlease-chess</a></p>