A little helper to unit test Vue components in the open source Cypress.io E2E test runner v4.5.0+
Jump to: Comparison, Blog posts, Examples: basic, advanced, full, external, Code coverage
How is this different from vue-test-utils? Vue Test Utils uses Node, requires stubbing browser APIs, and requires users to await Vue’s internal event loop. Cypress Vue Unit Test runs each component in the real browser with full power of Cypress E2E test runner: live GUI, full API, screen recording, CI support, cross-platform.
If you like using @testing-library/vue
, you can use @testing-library/cypress
for the same findBy
, queryBy
commands, see one of the examples in the list below
Vue CLI v3+
Recommended: One step install to existing projects with Vue CLI via experimental plugin, read Write Your First Vue Component Test
vue add cypress-experimental
If you want to install this package manually, follow manual install
// components/HelloWorld.spec.js
import { mount } from 'cypress-vue-unit-test'
import { HelloWorld } from './HelloWorld.vue'
describe('HelloWorld component', () => {
it('works', () => {
mount(HelloWorld)
// now use standard Cypress commands
cy.contains('Hello World!').should('be.visible')
})
})
You can pass additional styles, css files and external stylesheets to load, see docs/styles.md for full list.
import Todo from './Todo.vue'
const todo = {
id: '123',
title: 'Write more tests',
}
mount(Todo, {
propsData: { todo },
stylesheets: [
'https://cdnjs.cloudflare.com/ajax/libs/bulma/0.7.2/css/bulma.css',
],
})
See examples below for details.
You can pass extensions (global components, mixins, modules to use) when mounting Vue component. Use { extensions: { ... }}
object inside the options
.
components
- object of ‘id’ and components to register globally, see Components exampleuse
(alias plugins
) - list of plugins, see Pluginsmixin
(alias mixins
) - list of global mixins, see Mixins examplefilters
- hash of global filters, see Filters exampleTake a look at the first Vue v2 example: Declarative Rendering. The code is pretty simple
<div id="app">
{{ message }}
</div>
var app = new Vue({
el: '#app',
data() {
return { message: 'Hello Vue!' }
},
})
It shows the message when running in the browser
Hello Vue!
Let’s test it in Cypress.io (for the current version see cypress/integration/spec.js).
import { mountCallback } from 'cypress-vue-unit-test'
describe('Declarative rendering', () => {
// Vue code from https://vuejs.org/v2/guide/#Declarative-Rendering
const template = `
<div id="app">
{{ message }}
</div>
`
const data = {
message: 'Hello Vue!',
}
// that's all you need to do
beforeEach(mountCallback({ template, data }))
it('shows hello', () => {
cy.contains('Hello Vue!')
})
it('changes message if data changes', () => {
// mounted Vue instance is available under Cypress.vue
Cypress.vue.message = 'Vue rocks!'
cy.contains('Vue rocks!')
})
})
Fire up Cypress test runner and have real browser (Electron, Chrome) load Vue and mount your test code and be able to interact with the instance through the reference Cypress.vue.$data
and via GUI. The full power of the Cypress API is available.
There is a list example next in the Vue docs.
<div id="app-4">
<ol>
<li v-for="todo in todos">
{{ todo.text }}
</li>
</ol>
</div>
var app4 = new Vue({
el: '#app-4',
data: {
todos: [
{ text: 'Learn JavaScript' },
{ text: 'Learn Vue' },
{ text: 'Build something awesome' },
],
},
})
Let’s test it. Simple.
import { mountCallback } from 'cypress-vue-unit-test'
describe('Declarative rendering', () => {
// List example from https://vuejs.org/v2/guide/#Declarative-Rendering
const template = `
<ol>
<li v-for="todo in todos">
{{ todo.text }}
</li>
</ol>
`
function data() {
return {
todos: [
{ text: 'Learn JavaScript' },
{ text: 'Learn Vue' },
{ text: 'Build something awesome' },
],
}
}
beforeEach(mountCallback({ template, data }))
it('shows 3 items', () => {
cy.get('li').should('have.length', 3)
})
it('can add an item', () => {
Cypress.vue.todos.push({ text: 'Test using Cypress' })
cy.get('li').should('have.length', 4)
})
})
The next section in the Vue docs starts with reverse message example.
<div id="app-5">
<p>{{ message }}</p>
<button v-on:click="reverseMessage">Reverse Message</button>
</div>
var app5 = new Vue({
el: '#app-5',
data: {
message: 'Hello Vue.js!',
},
methods: {
reverseMessage: function () {
this.message = this.message.split('').reverse().join('')
},
},
})
We can write the test the same way
import { mountCallback } from 'cypress-vue-unit-test'
describe('Handling User Input', () => {
// Example from https://vuejs.org/v2/guide/#Handling-User-Input
const template = `
<div>
<p>{{ message }}</p>
<button v-on:click="reverseMessage">Reverse Message</button>
</div>
`
function data() {
return { message: 'Hello Vue.js!' }
}
const methods = {
reverseMessage: function () {
this.message = this.message.split('').reverse().join('')
},
}
beforeEach(mountCallback({ template, data, methods }))
it('reverses text', () => {
cy.contains('Hello Vue')
cy.get('button').click()
cy.contains('!sj.euV olleH')
})
})
Take a look at the video of the test. When you hover over the CLICK
step the test runner is showing before and after DOM snapshots. Not only that, the application is fully functioning, you can interact with the application because it is really running!
Let us test a complex example. Let us test a single file Vue component. Here is the Hello.vue file
<template>
<p>{{ greeting }} World!</p>
</template>
<script>
export default {
data() {
return {
greeting: 'Hello',
}
},
}
</script>
<style scoped>
p {
font-size: 2em;
text-align: center;
}
</style>
note to learn how to load Vue component files in Cypress, see Bundling section.
Do you want to interact with the component? Go ahead! Do you want to have multiple components? No problem!
import Hello from '../../components/Hello.vue'
import { mountCallback } from 'cypress-vue-unit-test'
describe('Several components', () => {
const template = `
<div>
<hello></hello>
<hello></hello>
<hello></hello>
</div>
`
const components = {
hello: Hello,
}
beforeEach(mountCallback({ template, components }))
it('greets the world 3 times', () => {
cy.get('p').should('have.length', 3)
})
})
Button counter component is used in several Vue doc examples
<template>
<button v-on:click="incrementCounter">{{ counter }}</button>
</template>
<script>
export default {
data() {
return {
counter: 0,
}
},
methods: {
incrementCounter: function () {
this.counter += 1
this.$emit('increment')
},
},
}
</script>
<style scoped>
button {
margin: 5px 10px;
padding: 5px 10px;
border-radius: 3px;
}
</style>
Let us test it - how do we ensure the event is emitted when the button is clicked? Simple - let us spy on the event, spying and stubbing is built into Cypress
import ButtonCounter from '../../components/ButtonCounter.vue'
import { mountCallback } from 'cypress-vue-unit-test'
describe('ButtonCounter', () => {
beforeEach(mountCallback(ButtonCounter))
it('starts with zero', () => {
cy.contains('button', '0')
})
it('increments the counter on click', () => {
cy.get('button').click().click().click().contains('3')
})
it('emits "increment" event on click', () => {
const spy = cy.spy()
Cypress.vue.$on('increment', spy)
cy.get('button')
.click()
.click()
.then(() => {
expect(spy).to.be.calledTwice
})
})
})
The component is really updating the counter in response to the click and is emitting an event.
The mount function automatically wraps XMLHttpRequest giving you an ability to intercept XHR requests your component might do. For full documentation see Network Requests. In this repo see components/AjaxList.vue and the corresponding tests cypress/integration/ajax-list-spec.js.
// component use axios to get list of users
created() {
axios.get(`https://jsonplaceholder.cypress.io/users?_limit=3`)
.then(response => {
// JSON responses are automatically parsed.
this.users = response.data
})
}
// test can observe, return mock data, delay and a lot more
beforeEach(mountCallback(AjaxList))
it('can inspect real data in XHR', () => {
cy.server()
cy.route('/users?_limit=3').as('users')
cy.wait('@users').its('response.body').should('have.length', 3)
})
it('can display mock XHR response', () => {
cy.server()
const users = [{id: 1, name: 'foo'}]
cy.route('GET', '/users?_limit=3', users).as('users')
cy.get('li').should('have.length', 1)
.first().contains('foo')
})
window.alert
Calls to window.alert
are automatically recorded, but do not show up. Instead you can spy on them, see AlertMessage.vue and its test cypress/integration/alert-spec.js
Feature | Vue Test Utils or @testing-library/vue | Cypress + cypress-vue-unit-test |
---|---|---|
Test runs in real browser | ❌ | ✅ |
Uses full mount | ❌ | ✅ |
Test speed | 🏎 | as fast as the app works in the browser |
Test can use additional plugins | maybe | use any Cypress plugin |
Test can interact with component | synthetic limited API | use any Cypress command |
Test can be debugged | via terminal and Node debugger | use browser DevTools |
Built-in time traveling debugger | ❌ | Cypress time traveling debugger |
Re-run tests on file or test change | ✅ | ✅ |
Test output on CI | terminal | terminal, screenshots, videos |
Tests can be run in parallel | ✅ | ✅ via parallelization |
Test against interface | if using @testing-library/vue |
✅ and can use @testing-library/cypress |
Spying and mocking | Jest mocks | Sinon library |
Code coverage | ✅ | ✅ |
// components/HelloWorld.spec.js
import { mount } from 'cypress-vue-unit-test'
import { HelloWorld } from './HelloWorld.vue'
describe('HelloWorld component', () => {
it('works', () => {
mount(HelloWorld)
// now use standard Cypress commands
cy.contains('Hello World!').should('be.visible')
})
})
Spec | Description |
---|---|
Components | Registers global components to use |
Filters | Registering global filters |
Hello | Testing examples from Vue2 cookbook |
Mixins | Registering Vue mixins |
Plugins | Loading additional plugins |
Props | Pass props to the component during mount |
Slots | Passing slots and scopedSlots to the component |
Small examples | A few small examples testing forms, buttons |
Spec | Description |
---|---|
access-component | Access the mounted component directly from test |
i18n | Testing component that uses Vue I18n plugin |
mocking-axios | Mocking 3rd party CommonJS modules like axios |
mocking-components | Mocking locally registered child components during tests |
mocking-imports | Stub ES6 imports from the tests |
render-functions | Mounting components with a render function |
We have several subfolders in examples folder.
Folder Name | Description |
---|---|
cli | An example app scaffolded using Vue CLI and the component testing added using vue add cypress-experimental command. |
Repo | Description |
---|---|
vue-component-test-example | Scaffolded Vue CLI v3 project with added component tests, read Write Your First Vue Component Test. |
How do we load this Vue file into the testing code? Using webpack preprocessor. Note that this module ships with @cypress/webpack-preprocessor 2.x that requires Webpack 4.x. If you have Webpack 3.x please add @cypress/webpack-preprocessor v1.x
.
Your project probably already has webpack.config.js
setup to transpile .vue
files. To load these files in the Cypress tests, grab the webpack processor included in this module, and load it from the cypress/plugins/index.js
file.
const {
onFilePreprocessor,
} = require('cypress-vue-unit-test/preprocessor/webpack')
module.exports = (on) => {
on('file:preprocessor', onFilePreprocessor('../path/to/webpack.config'))
}
Cypress should be able to import .vue
files in the tests
Using @cypress/webpack-preprocessor and vue-loader. You can use cypress/plugins/index.js to load .vue
files using vue-loader
.
// cypress/plugins/index.js
const webpack = require('@cypress/webpack-preprocessor')
const webpackOptions = {
module: {
rules: [
{
test: /\.vue$/,
loader: 'vue-loader',
},
],
},
}
const options = {
// send in the options from your webpack.config.js, so it works the same
// as your app's code
webpackOptions,
watchOptions: {},
}
module.exports = (on) => {
on('file:preprocessor', webpack(options))
}
Install dev dependencies
npm i -D @cypress/webpack-preprocessor \
vue-loader vue-template-compiler css-loader
And write a test
import Hello from '../../components/Hello.vue'
import { mountCallback } from 'cypress-vue-unit-test'
describe('Hello.vue', () => {
beforeEach(mountCallback(Hello))
it('shows hello', () => {
cy.contains('Hello World!')
})
})
This plugin uses babel-plugin-istanbul
to automatically instrument .js
and .vue
files and generates the code coverage report using dependency cypress-io/code-coverage (included). The output reports are saved in the folder “coverage” at the end of the test run.
If you want to disable code coverage instrumentation and reporting, use --env coverage=false
or CYPRESS_coverage=false
or set in your cypress.json
file
{
"env": {
"coverage": false
}
}
To see all local tests, install dependencies, build the code and open Cypress in GUI mode
npm install
npm run build
npm run cy:open
The build is done using tsc
that transpiles all files from src to dist
folder.
Run Cypress with environment variable
DEBUG=cypress-vue-unit-test
If some deeply nested objects are abbreviated and do not print fully, set the maximum logging depth
DEBUG=cypress-vue-unit-test DEBUG_DEPTH=10
cypress/plugins/index.js
file to pass the on, config
arguments when creating the default preprocessor. See change, in general the new way is:const {
onFileDefaultPreprocessor,
} = require('cypress-vue-unit-test/preprocessor/webpack')
module.exports = (on, config) => {
require('@cypress/code-coverage/task')(on, config)
on('file:preprocessor', onFileDefaultPreprocessor(config))
// IMPORTANT to return the config object
// with the any changed environment variables
return config
}
Author: bahmutov
GitHub: https://github.com/bahmutov/cypress-vue-unit-test
#vuejs #vue #javascript #vue-js