chai

Chai is a BDD / TDD assertion library for node and the browser that can be delightfully paired with any javascript testing framework.

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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

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chai is available on npm. To install it, type:

$ npm install --save-dev chai

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You can also use it within the browser; install via npm and use the chai.js file found within the download. For example:

``html

`

Usage

Import the library in your code, and then pick one of the styles you'd like to use - either assert, expect or should:

`js
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
`

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`js
require('chai/register-assert'); // Using Assert style
require('chai/register-expect'); // Using Expect style
require('chai/register-should'); // Using Should style
`

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`js
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
`

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`js
import 'chai/register-assert'; // Using Assert style
import 'chai/register-expect'; // Using Expect style
import 'chai/register-should'; // Using Should style
`

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`js
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
`

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`bash
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-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

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- 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 / 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.

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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.js` build. We do it once per release.
- Before pushing your commits, please make sure you rebase them.

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Please see the full
Contributors Graph for our
list of contributors.

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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.