chai

<h1 align=center> <a href="http://chaijs.com" title="Chai Documentation"> <img alt="ChaiJS" src="http://chaijs.com/img/chai-logo.png"> </a> <br> chai </h1> <p align=center> Chai is a BDD / TDD assertion library for <a href="http://nodejs.org">node</a> and the browser that can be delightfully paired with any javascript testing framework. </p> <p align=center> <a href="https://www.npmjs.com/package/chai"> <img alt="downloads:?" src="https://img.shields.io/npm/dm/chai.svg?style=flat-square" /> </a> <a href="https://www.npmjs.com/package/chai"> <img alt="node:?" src="https://img.shields.io/badge/node-%3E=4.0-blue.svg?style=flat-square" /> </a> <br/> <a href="https://chai-slack.herokuapp.com/"> <img alt="Join the Slack chat" src="https://img.shields.io/badge/slack-join%20chat-E2206F.svg?style=flat-square" /> </a> <a href="https://gitter.im/chaijs/chai"> <img alt="Join the Gitter chat" src="https://img.shields.io/badge/gitter-join%20chat-D0104D.svg?style=flat-square" /> </a> <a href="https://opencollective.com/chaijs"> <img alt="OpenCollective Backers" src="https://opencollective.com/chaijs/backers/badge.svg?style=flat-square" /> </a> </p>

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 --save-dev 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:

import { assert } from 'chai';  // Using Assert style
import { expect } from 'chai';  // Using Expect style
import { should } from 'chai';  // Using Should style

Register 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

Import assertion styles as local variables

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`

import { expect, use } from 'chai';  // Creates local variables `expect` and `use`; useful for plugin use

Usage with Mocha

mocha spec.js --require chai/register-assert.js  # Using Assert style
mocha spec.js --require chai/register-expect.js  # Using Expect style
mocha spec.js --require chai/register-should.js  # Using Should style

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-plugin
- browser if your plugin works in the browser as well as Node.js
- browser-only if your plugin does not work with Node.js

Related Projects

chaijs / chai-docs: The chaijs.com website source code.
chaijs / assertion-error: Custom Error constructor thrown upon an assertion failing.
chaijs / deep-eql: Improved deep equality testing 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.