chai

What is chai?

Chai is a BDD / TDD assertion library for node and the browser that can be delightfully paired with any javascript testing framework. It provides functions to express assertions in a readable language, supporting both 'should' and 'expect' style syntaxes, as well as a traditional 'assert' style interface.

What are chai's main functionalities?

Should Style Assertions

Allows you to write assertions in a more human-readable form, which reads like English. The 'should' style extends each object with a 'should' property to start your chain.

chai.should();
var should = chai.should();
should.exist(value, 'value should not be null or undefined');

Expect Style Assertions

Provides a function called 'expect' to make assertions about values. This style is similar to 'should' but does not extend any objects, which is useful for working with libraries that don't allow object extensions.

var expect = chai.expect;
expect(value).to.exist.and.be.an('object');

Assert Style Assertions

Offers a more traditional testing interface, which is similar to Node.js' core 'assert' module but with more capabilities and better error messages.

var assert = chai.assert;
assert.typeOf(value, 'string', 'value is a string');

Chainable Language Chains

Provides chainable getters to improve the readability of your assertions, allowing you to write more expressive tests.

expect(value).to.be.an('array').that.includes(3);

Plugins

Supports plugins to extend its core functionalities, which can be used to add new assertions, matchers, or methods to the library.

var chaiHttp = require('chai-http');
chai.use(chaiHttp);

Other packages similar to chai

jest

Jest is a delightful JavaScript Testing Framework with a focus on simplicity. It works out of the box for any React project and includes its own assertion library, which provides a similar but more integrated testing experience compared to Chai.

jasmine

Jasmine is a behavior-driven development framework for testing JavaScript code. It does not rely on browsers, DOM, or any JavaScript framework, making it suitable for websites, Node.js projects, or anywhere JavaScript can run. It has its own assertion syntax that is somewhat similar to Chai's 'expect' syntax.

expect.js

Expect.js is a minimalistic BDD-style assertions library that can be considered an alternative to Chai's 'expect' interface. It provides a similar API but is no longer actively maintained.

README

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

For more information or to download plugins, view the documentation.

Plugins

Chai offers a robust Plugin architecture for extending Chai's assertions and interfaces.

• Need a plugin? View the official plugin list.
• Have a plugin and want it listed? Open a Pull Request at chaijs/chai-docs:plugin.js.
• Want to build a plugin? Read the plugin api documentation.

Related Projects

• 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.

Contributing

Thank you very much for considering to contribute!

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.

We also strongly encourage you to read our detailed contribution guidelines.

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 you questions or concerns. We will do our best to respond in a timely manner.

License

(The MIT License)

Copyright (c) 2011-2015 Jake Luer [e-mail]

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.