title: Two shallowmount throw error Jest VueJs(Vuetify)
body: <p>I'm using VueJs with Vuetify and I want to test my Component: </p>
  
  <pre><code>import { shallowMount, createLocalVue } from '@vue/test-utils'
  import UserRating from '@/views/dashboard/pages/User_Ratings.vue'
  import BaseMaterialCard from '@/components/base/MaterialCard'
  import Vuetify from 'vuetify'
  let localVue
  
  describe('user ratings Component Unit test', () =&gt; {
    let vuetify
    beforeEach(() =&gt; {
      localVue = createLocalVue()
      vuetify = new Vuetify()
      localVue.use(vuetify)
    })
    it('is a Vue instance', () =&gt; {
      const msg = 'new message'
      const wrapper = shallowMount(UserRating, {
        localVue,
        vuetify,
        sync: false,
        propsData: { msg },
      })
  
      expect(wrapper.isVueInstance()).toBeTruthy()
    })
    it('Checks the data-title', () =&gt; {
      const wrapper = shallowMount(UserRating, {
        localVue,
        vuetify,
        sync: false,
      })
      expect(wrapper.vm.title).toMatch('Users Reviews')
    })
    it('renders the reviews list', () =&gt; {
      const wrapper = shallowMount(UserRating, {
        localVue,
        vuetify,
        sync: false,
      })
      expect(wrapper.html()).toContain('v-simple-table')
    })
    it('check if child BaseMaterialCard exists', () =&gt; {
      const wrapper = shallowMount(UserRating, {
        sync: false,
      })
      expect(wrapper.contains(BaseMaterialCard)).toBe(true)
    })
  })
  </code></pre>
  
  <p>I tried the solution in : <a href="https://stackoverflow.com/questions/59070770/testing-vuetify-vue-js-second-call-on-mount-throws-error">Testing Vuetify (Vue.js) - Second call on mount throws error</a>
  but when I run each test independently I got no problem but when I use npm run test or jest I got the tests running with an error : </p>
  
  <blockquote>
    <p>console.error node_modules/vue/dist/vue.runtime.common.dev.js:1884
        TypeError: Cannot set property '_error' of undefined
     console.error node_modules/vue/dist/vue.runtime.common.dev.js:621
        [Vue warn]: Error in nextTick: "TypeError: Cannot read property 'createElement' of null"</p>
  </blockquote>