react-testing-library
Simple and complete React DOM testing utilities that encourage good testing practices.
Table of Contents
- The problem
- This solution
- Example
- Installation
- Examples
- Other Solutions
- Guiding Principles
- Contributors
- Issues
- 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.
This solution
The react-testing-library is a very light-weight 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.
Example
// __tests__/fetch.js
import React from 'react'
import {render, fireEvent, cleanup, waitForElement} from 'react-testing-library'
// this adds custom jest matchers from jest-dom
import 'jest-dom/extend-expect'
// the mock lives in a __mocks__ directory
// to know more about manual mocks, access: https://jestjs.io/docs/en/manual-mocks
import axiosMock from 'axios'
import Fetch from '../fetch' // see the tests for a full implementation
// automatically unmount and cleanup DOM after the test is finished.
afterEach(cleanup)
test('Fetch makes an API call and displays the greeting when load-greeting is clicked', async () => {
// Arrange
axiosMock.get.mockResolvedValueOnce({data: {greeting: 'hello there'}})
const url = '/greeting'
const {getByText, getByTestId, container, asFragment} = render(
<Fetch url={url} />,
)
// Act
fireEvent.click(getByText(/load greeting/i))
// Let's wait until our mocked `get` request promise resolves and
// the component calls setState and re-renders.
// getByTestId throws an error if it cannot find an element with the given ID
// and waitForElement will wait until the callback doesn't throw an error
const greetingTextNode = await waitForElement(() =>
getByTestId('greeting-text'),
)
// Assert
expect(axiosMock.get).toHaveBeenCalledTimes(1)
expect(axiosMock.get).toHaveBeenCalledWith(url)
expect(getByTestId('greeting-text')).toHaveTextContent('hello there')
expect(getByTestId('ok-button')).toHaveAttribute('disabled')
// snapshots work great with regular DOM nodes!
expect(container.firstChild).toMatchSnapshot()
// you can also use get a `DocumentFragment`, which is useful if you want to compare nodes across render
expect(asFragment()).toMatchSnapshot()
})Installation
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 react-testing-library
This library has peerDependencies listings for react and react-dom.
You may also be interested in installing jest-dom so you can use
the custom jest matchers.
Examples
We're in the process of moving examples to the docs site
You'll find runnable examples of testing with different libraries in
the examples directory.
Some included are:
react-reduxreact-routerreact-contextreact-hooks- Use react-testing-library to test a custom React Hook.
You can also find react-testing-library examples at react-testing-examples.com.
Other Solutions
In preparing this project, I tweeted about it and Sune Simonsen took up the challenge. We had different ideas of what to include in the library, so I decided to create this one instead.
Guiding Principles
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:
- If it relates to rendering components, it deals with DOM nodes rather than component instances, nor should it encourage dealing with component instances.
- 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 toreact-dom. - Utility implementations and APIs should be simple and flexible.
At the end of the day, what we want is for this library to be pretty light-weight, simple, and understandable.
Contributors
Thanks goes to these people (emoji key):
This project follows the all-contributors specification. Contributions of any kind welcome!
Issues
Looking to contribute? Look for the Good First Issue label.
π Bugs
Please file an issue for bugs, missing documentation, or unexpected behavior.
π‘ Feature Requests
Please file an issue to suggest new features. Vote on feature requests by adding a π. This helps maintainers prioritize what to work on.
β Questions
For questions related to using the library, please visit a support community instead of filing an issue on GitHub.
LICENSE
MIT