title: Webpack External dependencies and jest
body: <p>I'm using a webpack external dependency</p>
  
  <pre><code>// wepack.config.dev.js
  externals: {
      amdRequire: 'require'
  }
  
  // component.js
  
  import amdRequire from 'amdRequire'
  
  //component.test.js
  
  shallow(&lt;component/&gt;
  /*Basic test*/
  </code></pre>
  
  <p>I get this error</p>
  
  <pre><code>Cannot find module 'amdRequire' from 'component.js'
      at Resolver.resolveModule (node_modules/jest-resolve/build/index.js:179:17)
  </code></pre>
  
  <p>I been trying a way to mock this external dependencies. 
  I tried using the below setup without much luck</p>
  
  <ol>
  <li>Jest-webpack-resolver</li>
  <li>create a file in <em>mock</em> folder</li>
  <li>adding global.amdRequire in a file and adding the file in package.json -> jest -> setupFiles</li>
  </ol>