docs: update common-tips.md (#1290)

Author: atilacamurca

Diff for: docs/guides/common-tips.md

@@ -143,7 +143,7 @@ Some of the components may rely on features injected by a global plugin or mixin
 If you are writing tests for components in a specific app, you can setup the same global plugins and mixins once in the entry of your tests. But in some cases, for example testing a generic component suite that may get shared across different apps, it's better to test your components in a more isolated setup, without polluting the global `Vue` constructor. We can use the [`createLocalVue`](../api/createLocalVue.md) method to achieve that:
 
 ```js
-import { createLocalVue } from '@vue/test-utils'
+import { createLocalVue, mount } from '@vue/test-utils'
 
 // create an extended `Vue` constructor
 const localVue = createLocalVue()