title: vue test utils TypeError: Cannot destructure property `config` of 'undefined' or 'null'
body: <p>I'm doing just simple unit test with vue test utils.
  but It's not working.
  I've no clue....
  help me</p>
  <p>I installed this things.....</p>
  <pre><code>&gt; $ npm i -D jest @vue/test-utils vue-jest jest-serializer-vue babel-jest babel-core@bridge
  
  &gt; $ npm i -D @babel/core @babel/preset-env
  </code></pre>
  <p>I made <em>jest.config.js</em> file</p>
  <pre><code>module.exports = {
    moduleFileExtensions: [
      'vue',
      'js'
    ],
  
    moduleNameMapper: {
      '^~/(.*)$': '&lt;rootDir&gt;/src/$1'
    },
  
    modulePathIgnorePatterns: [
      '&lt;rootDir&gt;/node_modules',
      '&lt;rootDir&gt;/dist'
    ],
  
    testURL: 'http://localhost',
  
    transform: {
      '^.+\\.vue$' : 'vue-jest',
      '^.+\\.jsx?$' : 'babel-jest'
    }
  }
  </code></pre>
  <p>and tests/Parent.test.js</p>
  <pre><code>import { mount } from '@vue/test-utils'
  import Parent from './Parent.vue'
  
  test('Mount', () =&gt; {
    const wrapper = mount(Parent)
    expect(wrapper.html()).toBe('')
  })
  </code></pre>
  <p>but npm run test:unit error like this</p>
  <pre><code> FAIL  tests/Parent.test.js
    ● Test suite failed to run
  
      TypeError: Cannot destructure property `config` of 'undefined' or 'null'.
  
        at Object.getCacheKey (node_modules/vue-jest/lib/index.js:10:5)
        at ScriptTransformer._getCacheKey (node_modules/@jest/transform/build/ScriptTransformer.js:280:41)
        at ScriptTransformer._getFileCachePath (node_modules/@jest/transform/build/ScriptTransformer.js:351:27)
        at ScriptTransformer.transformSource (node_modules/@jest/transform/build/ScriptTransformer.js:588:32)
        at ScriptTransformer._transformAndBuildScript (node_modules/@jest/transform/build/ScriptTransformer.js:758:40)
        at ScriptTransformer.transform (node_modules/@jest/transform/build/ScriptTransformer.js:815:19)
  
  Test Suites: 1 failed, 1 total
  Tests:       0 total
  Snapshots:   0 total
  Time:        0.512 s
  Ran all test suites.
  </code></pre>