# jest
**Repository Path**: mirrors_buger/jest
## Basic Information
- **Project Name**: jest
- **Description**: Delightful JavaScript Testing.
- **Primary Language**: Unknown
- **License**: MIT
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No
## Statistics
- **Stars**: 0
- **Forks**: 0
- **Created**: 2020-09-24
- **Last Updated**: 2026-01-17
## Categories & Tags
**Categories**: Uncategorized
**Tags**: None
## README
Jest
🃏 Delightful JavaScript Testing
**👩🏻💻 Developer Ready**: Complete and ready to set-up JavaScript testing solution. Works out of the box for any React project.
**🏃🏽 Instant Feedback**: Fast interactive watch mode runs only test files related to changed files and is optimized to give signal quickly.
**📸 Snapshot Testing**: Capture snapshots of React trees or other serializable values to simplify testing and to analyze how state changes over time.
## Getting Started
Install Jest using [`yarn`](https://yarnpkg.com/en/package/jest):
```bash
yarn add --dev jest
```
Or via [`npm`](https://www.npmjs.com/):
```bash
npm install --save-dev jest
```
The minimum supported Node version is `v6.0.0` by default. If you need to support Node 4, refer to the [Compatibility issues](https://jestjs.io/docs/en/troubleshooting#compatibility-issues) section.
Let's get started by writing a test for a hypothetical function that adds two numbers. First, create a `sum.js` file:
```javascript
function sum(a, b) {
return a + b;
}
module.exports = sum;
```
Then, create a file named `sum.test.js`. This will contain our actual test:
```javascript
const sum = require('./sum');
test('adds 1 + 2 to equal 3', () => {
expect(sum(1, 2)).toBe(3);
});
```
Add the following section to your `package.json`:
```json
{
"scripts": {
"test": "jest"
}
}
```
Finally, run `yarn test` and Jest will print this message:
```bash
PASS ./sum.test.js
✓ adds 1 + 2 to equal 3 (5ms)
```
**You just successfully wrote your first test using Jest!**
This test used `expect` and `toBe` to test that two values were exactly identical. To learn about the other things that Jest can test, see [Using Matchers](https://jestjs.io/docs/using-matchers).
## Running from command line
You can run Jest directly from the CLI (if it's globally available in your `PATH`, e.g. by `yarn global add jest`) with variety of useful options.
Here's how to run Jest on files matching `my-test`, using `config.json` as a configuration file and display a native OS notification after the run:
```bash
jest my-test --notify --config=config.json
```
If you'd like to learn more about running `jest` through the command line, take a look at the [Jest CLI Options](https://jestjs.io/docs/cli) page.
## Additional Configuration
### Using Babel
To use [Babel](http://babeljs.io/), install the `babel-jest` and `@babel/core` packages:
```bash
yarn add --dev babel-jest @babel/core
```
Don't forget to add a [`babel.config.js`](https://babeljs.io/docs/en/config-files) file in your project's root folder. For example, if you are using ES6 and [React.js](https://reactjs.org) with the [`@babel/preset-env`](https://babeljs.io/docs/en/babel-preset-env) and [`@babel/preset-react`](https://babeljs.io/docs/en/babel-preset-react) presets:
```js
module.exports = {
presets: ['@babel/preset-env', '@babel/preset-react'],
};
```
You are now set up to use all ES6 features and React specific syntax.
> Note: `babel-jest` is automatically installed when installing Jest and will automatically transform files if a babel configuration exists in your project. To avoid this behavior, you can explicitly reset the `transform` configuration option:
```json
// package.json
{
"jest": {
"transform": {}
}
}
```
### Using webpack
Jest can be used in projects that use [webpack](https://webpack.js.org/) to manage assets, styles, and compilation. webpack does offer some unique challenges over other tools. Refer to the [webpack guide](docs/Webpack.md) to get started.
### Using TypeScript
To use TypeScript in your tests install `@babel/preset-typescript` and add it to your Babel config.
## Documentation
Learn more about using [Jest on the official site!](https://jestjs.io)
- [Getting Started](https://jestjs.io/docs/en/getting-started)
- [Guides](https://jestjs.io/docs/en/snapshot-testing)
- [API Reference](https://jestjs.io/docs/en/api)
- [Configuring Jest](https://jestjs.io/docs/en/configuration)
## Badge
Show the world you're using _Jest_ → [](https://github.com/facebook/jest) [](https://github.com/facebook/jest)
```md
[](https://github.com/facebook/jest) [](https://github.com/facebook/jest)
```
## Contributing
Development of Jest happens in the open on GitHub, and we are grateful to the community for contributing bugfixes and improvements. Read below to learn how you can take part in improving Jest.
### [Code of Conduct](https://code.facebook.com/codeofconduct)
Facebook has adopted a Code of Conduct that we expect project participants to adhere to. Please read [the full text](https://code.facebook.com/codeofconduct) so that you can understand what actions will and will not be tolerated.
### [Contributing Guide](CONTRIBUTING.md)
Read our [contributing guide](CONTRIBUTING.md) to learn about our development process, how to propose bugfixes and improvements, and how to build and test your changes to Jest.
### [Good First Issues](https://github.com/facebook/jest/labels/%3Awave%3A%20Good%20First%20Issue)
To help you get your feet wet and get you familiar with our contribution process, we have a list of [good first issues](https://github.com/facebook/jest/labels/%3Awave%3A%20Good%20First%20Issue) that contain bugs which have a relatively limited scope. This is a great place to get started.
## Credits
This project exists thanks to all the people who [contribute](CONTRIBUTING.md). 
### [Backers](https://opencollective.com/jest#backer)
Thank you to all our backers! 🙏
### [Sponsors](https://opencollective.com/jest#sponsor)
Support this project by becoming a sponsor. Your logo will show up here with a link to your website.
## License
Jest is [MIT licensed](./LICENSE).