# React Testing Library

Simple and complete React DOM testing utilities that encourage good testing practices.

[**Read The Docs**](https://testing-library.com/react) | [Edit the docs](https://github.com/testing-library/testing-library-docs)

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## Table of Contents - [The problem](#the-problem) - [The solution](#the-solution) - [Installation](#installation) - [Suppressing unnecessary warnings on React DOM 16.8](#suppressing-unnecessary-warnings-on-react-dom-168) - [Examples](#examples) - [Basic Example](#basic-example) - [Complex Example](#complex-example) - [More Examples](#more-examples) - [Hooks](#hooks) - [Guiding Principles](#guiding-principles) - [Docs](#docs) - [Issues](#issues) - [🐛 Bugs](#-bugs) - [💡 Feature Requests](#-feature-requests) - [❓ Questions](#-questions) - [Contributors](#contributors) - [LICENSE](#license) ## The problem 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 solution 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.][guiding-principle] ## Installation This module is distributed via [npm][npm] which is bundled with [node][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] ``` 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](https://github.com/testing-library/jest-dom). > [**Docs**](https://testing-library.com/react) ### Suppressing unnecessary warnings on React DOM 16.8 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](https://github.com/testing-library/react-testing-library/issues/281)): ```js // 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 }) ``` ## Examples ### Basic Example ```jsx // 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 (
Show Message setShowMessage(e.target.checked)} checked={showMessage} /> {showMessage ? children : null}
) } export default HiddenMessage ``` ```jsx // __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({testMessage}) // 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() }) ``` ### Complex Example ```jsx // 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 (
Username
Password
{state.error ?
{state.error}
: null} {state.resolved ? (
Congrats! You're signed in!
) : null}
) } export default Login ``` ```jsx // __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() // 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() // 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](https://github.com/mswjs/msw) library > to declaratively mock API communication in your tests instead of stubbing > `window.fetch`, or relying on third-party adapters. ### More Examples > We're in the process of moving examples to the > [docs site](https://testing-library.com/docs/example-codesandbox) You'll find runnable examples of testing with different libraries in [the `react-testing-library-examples` codesandbox](https://codesandbox.io/s/github/kentcdodds/react-testing-library-examples). Some included are: - [`react-redux`](https://codesandbox.io/s/github/kentcdodds/react-testing-library-examples/tree/main/?fontsize=14&module=%2Fsrc%2F__tests__%2Freact-redux.js&previewwindow=tests) - [`react-router`](https://codesandbox.io/s/github/kentcdodds/react-testing-library-examples/tree/main/?fontsize=14&module=%2Fsrc%2F__tests__%2Freact-router.js&previewwindow=tests) - [`react-context`](https://codesandbox.io/s/github/kentcdodds/react-testing-library-examples/tree/main/?fontsize=14&module=%2Fsrc%2F__tests__%2Freact-context.js&previewwindow=tests) You can also find React Testing Library examples at [react-testing-examples.com](https://react-testing-examples.com/jest-rtl/). ## Hooks If you are interested in testing a custom hook, check out [React Hooks Testing Library][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 Library` > is intended to be used for reusable hooks/libraries. ## Guiding Principles > [The more your tests resemble the way your software is used, the more > confidence they can give you.][guiding-principle] 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: 1. If it relates to rendering components, it deals with DOM nodes rather than component instances, nor should it encourage dealing with component instances. 2. It should be generally useful for testing individual React components or full React applications. While this library is focused on `react-dom`, utilities could be included even if they don't directly relate to `react-dom`. 3. Utility implementations and APIs should be simple and flexible. Most importantly, we want React Testing Library to be pretty light-weight, simple, and easy to understand. ## Docs [**Read The Docs**](https://testing-library.com/react) | [Edit the docs](https://github.com/testing-library/testing-library-docs) ## Issues Looking to contribute? Look for the [Good First Issue][good-first-issue] label. ### 🐛 Bugs Please file an issue for bugs, missing documentation, or unexpected behavior. [**See Bugs**][bugs] ### 💡 Feature Requests Please file an issue to suggest new features. Vote on feature requests by adding a 👍. This helps maintainers prioritize what to work on. [**See Feature Requests**][requests] ### ❓ Questions For questions related to using the library, please visit a support community instead of filing an issue on GitHub. - [Discord][discord] - [Stack Overflow][stackoverflow] ## Contributors Thanks goes to these people ([emoji key][emojis]):

Kent C. Dodds 💻 📖 🚇 ⚠️ | Ryan Castner 📖 | Daniel Sandiego 💻 | Paweł Mikołajczyk 💻 | Alejandro Ñáñez Ortiz 📖 | Matt Parrish 🐛 💻 📖 ⚠️ | Justin Hall 📦
Anto Aravinth 💻 ⚠️ 📖 | Jonah Moses 📖 | Łukasz Gandecki 💻 ⚠️ 📖 | Ivan Babak 🐛 🤔 | Jesse Day 💻 | Ernesto García 💬 💻 📖 | Josef Maxx Blake 💻 📖 ⚠️
Michal Baranowski 📝 ✅ | Arthur Puthin 📖 | Thomas Chia 💻 📖 | Thiago Galvani 📖 | Christian ⚠️ | Alex Krolick 💬 📖 💡 🤔 | Johann Hubert Sonntagbauer 💻 📖 ⚠️
Maddi Joyce 💻 | Ryan Vice 📖 | Ian Wilson 📝 ✅ | Daniel 🐛 💻 | Giorgio Polvara 🐛 🤔 | John Gozde 💻 | Sam Horton 📖 💡 🤔
Richard Kotze (mobile) 📖 | Brahian E. Soto Mercedes 📖 | Benoit de La Forest 📖 | Salah 💻 ⚠️ | Adam Gordon 🐛 💻 | Matija Marohnić 📖 | Justice Mba 📖
Mark Pollmann 📖 | Ehtesham Kafeel 💻 📖 | Julio Pavón 💻 | Duncan L 📖 💡 | Tiago Almeida 📖 | Robert Smith 🐛 | Zach Green 📖
dadamssg 📖 | Yazan Aabed 📝 | Tim 🐛 💻 📖 ⚠️ | Divyanshu Maithani ✅ 📹 | Deepak Grover ✅ 📹 | Eyal Cohen 📖 | Peter Makowski 📖
Michiel Nuyts 📖 | Joe Ng'ethe 💻 📖 | Kate 📖 | Sean 📖 | James Long 🤔 📦 | Herb Hagely 💡 | Alex Wendte 💡
Monica Powell 📖 | Vitaly Sivkov 💻 | Weyert de Boer 🤔 👀 🎨 | EstebanMarin 📖 | Victor Martins 📖 | Royston Shufflebotham 🐛 📖 💡 | chrbala 💻
Donavon West 💻 📖 🤔 ⚠️ | Richard Maisano 💻 | Marco Biedermann 💻 🚧 ⚠️ | Alex Zherdev 🐛 💻 | André Matulionis dos Santos 💻 💡 ⚠️ | Daniel K. 🐛 💻 🤔 ⚠️ 👀 | mohamedmagdy17593 💻
Loren ☺️ 📖 | MarkFalconbridge 🐛 💻 | Vinicius 📖 💡 | Peter Schyma 💻 | Ian Schmitz 📖 | Joel Marcotte 🐛 ⚠️ 💻 | Alejandro Dustet 🐛
Brandon Carroll 📖 | Lucas Machado 📖 | Pascal Duez 📦 | Minh Nguyen 💻 | LiaoJimmy 📖 | Sunil Pai 💻 ⚠️ | Dan Abramov 👀
Christian Murphy 🚇 | Ivakhnenko Dmitry 💻 | James George 📖 | João Fernandes 📖 | Alejandro Perea 👀 | Nick McCurdy 👀 💬 🚇 | Sebastian Silbermann 👀
Adrià Fontcuberta 👀 📖 | John Reilly 👀 | Michaël De Boey 👀 💻 | Tim Yates 👀 | Brian Donovan 💻 | Noam Gabriel Jacobson 📖 | Ronald van der Kooij ⚠️ 💻
Aayush Rajvanshi 📖 | Ely Alamillo 💻 ⚠️ | Daniel Afonso 💻 ⚠️ | Laurens Bosscher 💻 | Sakito Mukai 📖 | Türker Teke 📖 | Zach Brogan 💻 ⚠️
Ryota Murakami 📖 | Michael Hottman 🤔 | Steven Fitzpatrick 🐛 | Juan Je García 📖 | Championrunner 📖 | Sam Tsai 💻 ⚠️ 📖 | Christian Rackerseder 💻
Andrei Picus 🐛 👀 | Artem Zakharchenko 📖 | Michael 📖 | Braden Lee 📖 | Kamran Ayub 💻 ⚠️ | Matan Borenkraout 💻 | Ryan Bigg 🚧
Anton Halim 📖 | Artem Malko 💻 | Gerrit Alex 💻 | Karthick Raja 💻 | Abdelrahman Ashraf 💻 | Lidor Avitan 📖 | Jordan Harband 👀 🤔
Marco Moretti 💻 | sanchit121 🐛 💻 | Solufa 🐛 💻 | Ari Perkkiö ⚠️ | Johannes Ewald 💻 | Angus J. Pope 📖 | Dominik Lesch 📖
Marcos Gómez 📖 | Akash Shyam 🐛 | Fabian Meumertzheim 💻 🐛 | Sebastian Malton 🐛 💻 | Martin Böttcher 💻 | Dominik Dorfmeister 💻

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