# Plugins

Plugins add global-level functionality to Vue Test Utils' API. This is the official way to extend Vue Test Utils' API with custom logic, methods, or functionality.

If you're missing a bit of functionality, consider writing a plugin to extend Vue Test Utils' API.

Some use cases for plugins:

  1. Aliasing existing public methods
  2. Attaching matchers to the Wrapper instance
  3. Attaching functionality to the Wrapper

# Using a Plugin

Install plugins by calling the config.plugins.VueWrapper.install() method . This has to be done before you call mount.

The install() method will receive an instance of WrapperAPI containing both public and private properties of the instance.

// setup.js file
import { config } from '@vue/test-utils'

// locally defined plugin, see "Writing a Plugin"
import MyPlugin from './myPlugin'

// Install a plugin onto VueWrapper
config.plugins.VueWrapper.install(MyPlugin)

You can optionally pass in some options:

config.plugins.VueWrapper.install(MyPlugin, { someOption: true })

Your plugin should be installed once. If you are using Jest, this should be in your Jest config's setupFiles or setupFilesAfterEnv file.

Some plugins automatically call config.plugins.VueWrapper.install() when they're imported. This is common if they're extending multiple interfaces at once. Follow the instructions of the plugin you're installing.

Check out the Vue Community Guide or awesome-vue for a collection of community-contributed plugins and libraries.

# Writing a Plugin

A Vue Test Utils plugin is simply a function that receives the mounted VueWrapper or DOMWrapper instance and can modify it.

# Basic Plugin

Below is a simple plugin to add a convenient alias to map wrapper.element to wrapper.$el

// setup.js
import { config } from '@vue/test-utils'

const myAliasPlugin = (wrapper) => {
  return {
    $el: wrapper.element // simple aliases
  }
}

// Call install on the type you want to extend
// You can write a plugin for any value inside of config.plugins
config.plugins.VueWrapper.install(myAliasPlugin)

And in your spec, you'll be able to use your plugin after mount.

// component.spec.js
const wrapper = mount({ template: `<h1>🔌 Plugin</h1>` })
console.log(wrapper.$el.innerHTML) // 🔌 Plugin

# Data Test ID Plugin

The below plugin adds a method findByTestId to the VueWrapper instance. This encourages using a selector strategy relying on test-only attributes on your Vue Components.

Usage:

MyComponent.vue:

<template>
  <MyForm class="form-container" data-testid="form">
    <MyInput data-testid="name-input" v-model="name"/>
  </MyForm>
</template>

MyComponent.spec.js:

const wrapper = mount(MyComponent)
wrapper.findByTestId('name-input') // returns a VueWrapper or DOMWrapper

Implementation of the plugin:

import { config } from '@vue/test-utils-next'

const DataTestIdPlugin = (wrapper) => {
  function findByTestId(selector) {
    const dataSelector = `[data-testid='${selector}']`
    const element = wrapper.element.querySelector(dataSelector)
    if (element) {
      return new DOMWrapper(element)
    }

    return createWrapperError('DOMWrapper')
  }

  return {
    findByTestId
  }
}

config.plugins.VueWrapper.install(DataTestIdPlugin)

# Featuring Your Plugin

If you're missing functionality, consider writing a plugin to extend Vue Test Utils and submit it to be featured at Vue Community Guide or awesome-vue.