docs: Improve approach for integration with Vuetify (#123)

* Alternative approach to preserve mountOptions

I suggest an alternative approach to the problem to preserve things like `props, propsData, updateProps` that are applied to the root node only.

* Add tests

* Fix comments

* Apply review suggestions

Co-authored-by: edgar.schnueriger <edgar.schnueriger@geopraevent.ch>

Author: Edgar Schnüriger

src/__tests__/components/Vuetify.vue

@@ -7,12 +7,19 @@
         <v-card-text>Lorem ipsum dolor sit amet.</v-card-text>
       </v-card>
     </v-dialog>
+    <span v-if="showHint">This is a hint</span>
   </v-app>
 </template>
 
 <script>
 export default {
   name: 'VuetifyDemoComponent',
+  props: {
+    showHint: {
+      type: Boolean,
+      default: false,
+    },
+  },
   data() {
     return {
       show: false,

src/__tests__/vuetify.js

@@ -1,3 +1,4 @@
+import '@testing-library/jest-dom'
 import Vue from 'vue'
 import {render, fireEvent} from '@testing-library/vue'
 import Vuetify from 'vuetify'
@@ -10,23 +11,18 @@ import VuetifyDemoComponent from './components/Vuetify'
 //            https://vuetifyjs.com/en/getting-started/unit-testing
 Vue.use(Vuetify)
 
-// Custom render wrapper to integrate Vuetify with Vue Testing Library.
+// Custom container to integrate Vuetify with Vue Testing Library.
 // Vuetify requires you to wrap your app with a v-app component that provides
 // a <div data-app="true"> node.
 const renderWithVuetify = (component, options, callback) => {
   return render(
-    // anonymous component
+    component,
     {
-      // Vue's render function
-      render(createElement) {
-        // wrap the component with a <div data-app="true"> node and render the test component
-        return createElement('div', {attrs: {'data-app': true}}, [
-          createElement(component),
-        ])
-      },
+      container: document.createElement('div').setAttribute('data-app', 'true'),
+      // for Vuetify components that use the $vuetify instance property
+      vuetify: new Vuetify(),
+      ...options,
     },
-    // for Vuetify components that use the $vuetify instance property
-    {vuetify: new Vuetify(), ...options},
     callback,
   )
 }
@@ -44,3 +40,13 @@ test('renders a Vuetify-powered component', async () => {
     </div>
   `)
 })
+
+test('allows changing props', async () => {
+  const {queryByText, updateProps} = renderWithVuetify(VuetifyDemoComponent)
+
+  expect(queryByText('This is a hint')).not.toBeInTheDocument()
+
+  await updateProps({showHint: true})
+
+  expect(queryByText('This is a hint')).toBeInTheDocument()
+})