@testing-library/react
Advanced tools
Simple and complete React DOM testing utilities that encourage good testing practices.
The @testing-library/react package is a set of utilities that allow you to work with React components in a way that simulates user interaction as closely as possible. It provides light utility functions on top of react-dom and react-dom/test-utils, in a way that encourages better testing practices. Its primary aim is to test the component the way users would. Therefore, it avoids including details about the component's internal structure, such as state or lifecycle methods, and instead focuses on making tests easy to write and understand.
Rendering Components
This feature allows you to render a React component into a container which is appended to document.body. It provides utility functions to interact with the rendered component.
import { render } from '@testing-library/react';
const { getByText } = render(<button>Click me</button>);
expect(getByText(/click me/i)).toBeInTheDocument();Querying Elements
Provides various methods to query elements from the rendered component, such as getByText, getByRole, etc., making it easier to assert their presence and properties.
import { screen } from '@testing-library/react';
render(<div>Hello World</div>);
expect(screen.getByText('Hello World')).toBeInTheDocument();User Events Simulation
Enables the simulation of user actions like clicking, typing, etc., on the rendered components. This is crucial for testing interactive elements.
import { render, fireEvent } from '@testing-library/react';
const { getByLabelText, getByText } = render(<label htmlFor='checkbox'>Check this box</label>
<input id='checkbox' type='checkbox' />);
fireEvent.click(getByText('Check this box'));
expect(getByLabelText('Check this box')).toBeChecked();Enzyme is a JavaScript Testing utility for React that makes it easier to test your React Components' output. It allows you to manipulate, traverse, and in some ways simulate runtime given the output. Enzyme's API is meant to be intuitive and flexible by mimicking jQuery's API for DOM manipulation and traversal. Compared to @testing-library/react, Enzyme provides more direct access to the component's internal structure, which can be both a strength and a weakness depending on the testing philosophy.
Cypress is a front-end testing tool built for the modern web. It is not limited to React alone but can test any web application. Its testing approach is somewhat different from @testing-library/react as it runs in a real browser and performs end-to-end testing. While @testing-library/react focuses on unit and integration tests from a user's perspective, Cypress provides a more comprehensive testing solution including full end-to-end testing capabilities.
Simple and complete React DOM testing utilities that encourage good testing practices.
You want to write maintainable tests for your React components. As a part of this goal, you want your tests to avoid including implementation details of your components and rather focus on making your tests give you the confidence for which they are intended. As part of this, you want your testbase to be maintainable in the long run so refactors of your components (changes to implementation but not functionality) don't break your tests and slow you and your team down.
The React Testing Library is a very lightweight solution for testing React
components. It provides light utility functions on top of react-dom and
react-dom/test-utils, in a way that encourages better testing practices. Its
primary guiding principle is:
The more your tests resemble the way your software is used, the more confidence they can give you.
This module is distributed via npm which is bundled with node and
should be installed as one of your project's devDependencies:
npm install --save-dev @testing-library/react
or
for installation via yarn
yarn add --dev @testing-library/react
This library has peerDependencies listings for react and react-dom.
You may also be interested in installing @testing-library/jest-dom so you can
use the custom jest matchers.
There is a known compatibility issue with React DOM 16.8 where you will see the following warning:
Warning: An update to ComponentName inside a test was not wrapped in act(...).
If you cannot upgrade to React DOM 16.9, you may suppress the warnings by adding the following snippet to your test configuration (learn more):
// this is just a little hack to silence a warning that we'll get until we
// upgrade to 16.9. See also: https://github.com/facebook/react/pull/14853
const originalError = console.error
beforeAll(() => {
console.error = (...args) => {
if (/Warning.*not wrapped in act/.test(args[0])) {
return
}
originalError.call(console, ...args)
}
})
afterAll(() => {
console.error = originalError
})
// hidden-message.js
import * as React from 'react'
// NOTE: React Testing Library works well with React Hooks and classes.
// Your tests will be the same regardless of how you write your components.
function HiddenMessage({children}) {
const [showMessage, setShowMessage] = React.useState(false)
return (
<div>
<label htmlFor="toggle">Show Message</label>
<input
id="toggle"
type="checkbox"
onChange={e => setShowMessage(e.target.checked)}
checked={showMessage}
/>
{showMessage ? children : null}
</div>
)
}
export default HiddenMessage
// __tests__/hidden-message.js
// these imports are something you'd normally configure Jest to import for you
// automatically. Learn more in the setup docs: https://testing-library.com/docs/react-testing-library/setup#cleanup
import '@testing-library/jest-dom'
// NOTE: jest-dom adds handy assertions to Jest and is recommended, but not required
import * as React from 'react'
import {render, fireEvent, screen} from '@testing-library/react'
import HiddenMessage from '../hidden-message'
test('shows the children when the checkbox is checked', () => {
const testMessage = 'Test Message'
render(<HiddenMessage>{testMessage}</HiddenMessage>)
// query* functions will return the element or null if it cannot be found
// get* functions will return the element or throw an error if it cannot be found
expect(screen.queryByText(testMessage)).toBeNull()
// the queries can accept a regex to make your selectors more resilient to content tweaks and changes.
fireEvent.click(screen.getByLabelText(/show/i))
// .toBeInTheDocument() is an assertion that comes from jest-dom
// otherwise you could use .toBeDefined()
expect(screen.getByText(testMessage)).toBeInTheDocument()
})
// login.js
import * as React from 'react'
function Login() {
const [state, setState] = React.useReducer((s, a) => ({...s, ...a}), {
resolved: false,
loading: false,
error: null,
})
function handleSubmit(event) {
event.preventDefault()
const {usernameInput, passwordInput} = event.target.elements
setState({loading: true, resolved: false, error: null})
window
.fetch('/api/login', {
method: 'POST',
headers: {'Content-Type': 'application/json'},
body: JSON.stringify({
username: usernameInput.value,
password: passwordInput.value,
}),
})
.then(r => r.json().then(data => (r.ok ? data : Promise.reject(data))))
.then(
user => {
setState({loading: false, resolved: true, error: null})
window.localStorage.setItem('token', user.token)
},
error => {
setState({loading: false, resolved: false, error: error.message})
},
)
}
return (
<div>
<form onSubmit={handleSubmit}>
<div>
<label htmlFor="usernameInput">Username</label>
<input id="usernameInput" />
</div>
<div>
<label htmlFor="passwordInput">Password</label>
<input id="passwordInput" type="password" />
</div>
<button type="submit">Submit{state.loading ? '...' : null}</button>
</form>
{state.error ? <div role="alert">{state.error}</div> : null}
{state.resolved ? (
<div role="alert">Congrats! You're signed in!</div>
) : null}
</div>
)
}
export default Login
// __tests__/login.js
// again, these first two imports are something you'd normally handle in
// your testing framework configuration rather than importing them in every file.
import '@testing-library/jest-dom'
import * as React from 'react'
// import API mocking utilities from Mock Service Worker.
import {rest} from 'msw'
import {setupServer} from 'msw/node'
// import testing utilities
import {render, fireEvent, screen} from '@testing-library/react'
import Login from '../login'
const fakeUserResponse = {token: 'fake_user_token'}
const server = setupServer(
rest.post('/api/login', (req, res, ctx) => {
return res(ctx.json(fakeUserResponse))
}),
)
beforeAll(() => server.listen())
afterEach(() => {
server.resetHandlers()
window.localStorage.removeItem('token')
})
afterAll(() => server.close())
test('allows the user to login successfully', async () => {
render(<Login />)
// fill out the form
fireEvent.change(screen.getByLabelText(/username/i), {
target: {value: 'chuck'},
})
fireEvent.change(screen.getByLabelText(/password/i), {
target: {value: 'norris'},
})
fireEvent.click(screen.getByText(/submit/i))
// just like a manual tester, we'll instruct our test to wait for the alert
// to show up before continuing with our assertions.
const alert = await screen.findByRole('alert')
// .toHaveTextContent() comes from jest-dom's assertions
// otherwise you could use expect(alert.textContent).toMatch(/congrats/i)
// but jest-dom will give you better error messages which is why it's recommended
expect(alert).toHaveTextContent(/congrats/i)
expect(window.localStorage.getItem('token')).toEqual(fakeUserResponse.token)
})
test('handles server exceptions', async () => {
// mock the server error response for this test suite only.
server.use(
rest.post('/api/login', (req, res, ctx) => {
return res(ctx.status(500), ctx.json({message: 'Internal server error'}))
}),
)
render(<Login />)
// fill out the form
fireEvent.change(screen.getByLabelText(/username/i), {
target: {value: 'chuck'},
})
fireEvent.change(screen.getByLabelText(/password/i), {
target: {value: 'norris'},
})
fireEvent.click(screen.getByText(/submit/i))
// wait for the error message
const alert = await screen.findByRole('alert')
expect(alert).toHaveTextContent(/internal server error/i)
expect(window.localStorage.getItem('token')).toBeNull()
})
We recommend using Mock Service Worker library to declaratively mock API communication in your tests instead of stubbing
window.fetch, or relying on third-party adapters.
We're in the process of moving examples to the docs site
You'll find runnable examples of testing with different libraries in
the react-testing-library-examples codesandbox.
Some included are:
You can also find React Testing Library examples at react-testing-examples.com.
If you are interested in testing a custom hook, check out React Hooks Testing Library.
NOTE: it is not recommended to test single-use custom hooks in isolation from the components where it's being used. It's better to test the component that's using the hook rather than the hook itself. The
React Hooks Testing Libraryis intended to be used for reusable hooks/libraries.
The more your tests resemble the way your software is used, the more confidence they can give you.
We try to only expose methods and utilities that encourage you to write tests that closely resemble how your React components are used.
Utilities are included in this project based on the following guiding principles:
react-dom,
utilities could be included even if they don't directly relate to
react-dom.Most importantly, we want React Testing Library to be pretty light-weight, simple, and easy to understand.
Looking to contribute? Look for the Good First Issue label.
Please file an issue for bugs, missing documentation, or unexpected behavior.
Please file an issue to suggest new features. Vote on feature requests by adding a ๐. This helps maintainers prioritize what to work on.
For questions related to using the library, please visit a support community instead of filing an issue on GitHub.
Thanks goes to these people (emoji key):
This project follows the all-contributors specification. Contributions of any kind welcome!
FAQs
Simple and complete React DOM testing utilities that encourage good testing practices.
We found that @testing-library/react demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago.ย It has 15 open source maintainers collaborating on the project.
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