title: Export on custom JS class causes error on in test using babel-jest
body: <p>In my Vue app test file I'm pulling in <code>import Users from '@/models/user';</code></p>
  
  <p>I've cleared the cache before running the test but it doesn't seem to help..</p>
  
  <p>In the <code>src/models/user.js</code> file I have: </p>
  
  <pre><code>export default class Users {
  
  }
  </code></pre>
  
  <p>When I run the test I get the error:</p>
  
  <pre><code>({"Object.&lt;anonymous&gt;":function(module,exports,require,__dirname,__filename,global,jest){export default function _classCallCheck(instance, Constructor) {
                                                                                           ^^^^^^
  
  SyntaxError: Unexpected token export
  
  
  
    at ScriptTransformer._transformAndBuildScript (node_modules/jest-runtime/build/script_transformer.js:403:17)
    at Object.&lt;anonymous&gt; (src/models/user.js:10:47)
  </code></pre>
  
  <p><code>jest.config.js</code> is as follows:</p>
  
  <pre><code>module.exports = {
    moduleFileExtensions: [
      'js',
      'jsx',
      'json',
      'vue'
    ],
    transform: {
      '^.+\\.vue$': 'vue-jest',
      '.+\\.(css|styl|less|sass|scss|svg|png|jpg|ttf|woff|woff2)$': 'jest-transform-stub',
      '^.+\\.jsx?$': 'babel-jest'
    },
    moduleNameMapper: {
      '^@/(.*)$': '&lt;rootDir&gt;/src/$1'
    },
    snapshotSerializers: [
      'jest-serializer-vue'
    ],
    testMatch: [
      '**/tests/unit/**/*.spec.(js|jsx|ts|tsx)|**/__tests__/*.(js|jsx|ts|tsx)'
    ],
    testURL: 'http://localhost/'
  }
  </code></pre>
  
  <p>and my <code>babel.config.js</code> is:</p>
  
  <pre><code>module.exports = {
    presets: [
      '@vue/app',
      '@babel/preset-env'
    ]
  }
  </code></pre>