Add custom Vuetify render wrapper to Vuetify test

src/__tests__/vuetify.js

@@ -5,21 +5,34 @@ import VuetifyDemoComponent from './components/Vuetify'
 
 // We need to use a global Vue instance, otherwise Vuetify will complain about
 // read-only attributes.
+// This could also be done in a custom Jest-test-setup file to execute for all tests.
 // More info: https://github.com/vuetifyjs/vuetify/issues/4068
 //            https://vuetifyjs.com/en/getting-started/unit-testing
 Vue.use(Vuetify)
 
-// Vuetify requires you to wrap you app with a v-app component that provides
-// a <div data-app="true"> node. So you can do that, or you can also set the
-// attribute to the DOM.
-document.body.setAttribute('data-app', true)
-// Another solution is to create a custom renderer that provides all the
-// environment required by Vuetify.
+// Custom render wrapper 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.
+export const renderWithVuetify = (component, options, callback) => {
+  return render(
+    // anonymous 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),
+        ])
+      },
+    },
+    // for Vuetify components that use the $vuetify instance property
+    {vuetify: new Vuetify(), ...options},
+    callback,
+  )
+}
 
 test('renders a Vuetify-powered component', async () => {
-  const {getByText} = render(VuetifyDemoComponent, {
-    vuetify: new Vuetify(),
-  })
+  const {getByText} = renderWithVuetify(VuetifyDemoComponent)
 
   await fireEvent.click(getByText('open'))