For more information or to download plugins, view the documentation.
What is Chai?
Chai is an assertion library, similar to Node's built-in assert. It makes testing much easier by giving you lots of assertions you can run against your code.
Installation
Node.js
chai is available on npm. To install it, type:
$ npm install chai
Browsers
You can also use it within the browser; install via npm and use the chai.js file found within the download. For example:
<script src="./node_modules/chai/chai.js"></script>
Usage
Import the library in your code, and then pick one of the styles you'd like to use - either assert, expect or should:
var chai = require('chai');
var assert = chai.assert; // Using Assert style
var expect = chai.expect; // Using Expect style
var should = chai.should(); // Using Should style
Pre-Native Modules Usage (registers the chai testing style globally)
require('chai/register-assert'); // Using Assert style
require('chai/register-expect'); // Using Expect style
require('chai/register-should'); // Using Should style
Pre-Native Modules Usage (as local variables)
const { assert } = require('chai'); // Using Assert style
const { expect } = require('chai'); // Using Expect style
const { should } = require('chai'); // Using Should style
should(); // Modifies `Object.prototype`
const { expect, use } = require('chai'); // Creates local variables `expect` and `use`; useful for plugin use
Native Modules Usage (registers the chai testing style globally)
import 'chai/register-assert'; // Using Assert style
import 'chai/register-expect'; // Using Expect style
import 'chai/register-should'; // Using Should style
Native Modules Usage (local import only)
import { assert } from 'chai'; // Using Assert style
import { expect } from 'chai'; // Using Expect style
import { should } from 'chai'; // Using Should style
should(); // Modifies `Object.prototype`
Usage with Mocha
mocha spec.js -r chai/register-assert # Using Assert style
mocha spec.js -r chai/register-expect # Using Expect style
mocha spec.js -r chai/register-should # Using Should style
Read more about these styles in our docs.
Plugins
Chai offers a robust Plugin architecture for extending Chai's assertions and interfaces.
- Need a plugin? View the official plugin list.
- Want to build a plugin? Read the plugin api documentation.
- Have a plugin and want it listed? Simply add the following keywords to your package.json:
chai-pluginbrowserif your plugin works in the browser as well as Node.jsbrowser-onlyif your plugin does not work with Node.js
Related Projects
- chaijs / chai-docs: The chaijs.com website source code.
- chaijs / assertion-error: Custom
Errorconstructor thrown upon an assertion failing. - chaijs / deep-eql: Improved deep equality testing for Node.js and the browser.
- chaijs / type-detect: Improved typeof detection for Node.js and the browser.
- chaijs / check-error: Error comparison and information related utility for Node.js and the browser.
- chaijs / loupe: Inspect utility for Node.js and browsers.
- chaijs / pathval: Object value retrieval given a string path.
- chaijs / get-func-name: Utility for getting a function's name for node and the browser.
Contributing
Thank you very much for considering to contribute!
Please make sure you follow our Code Of Conduct and we also strongly recommend reading our Contributing Guide.
Here are a few issues other contributors frequently ran into when opening pull requests:
- Please do not commit changes to the
chai.jsbuild. We do it once per release. - Before pushing your commits, please make sure you rebase them.
Contributors
Please see the full
Contributors Graph for our
list of contributors.
Core Contributors
Feel free to reach out to any of the core contributors with your questions or
concerns. We will do our best to respond in a timely manner.
