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 It provides a similar API but is no longer actively maintained.
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.
Related Projects
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 your questions or
concerns. We will do our best to respond in a timely manner.
License
(The MIT License)
Copyright (c) 2011-2015 Jake Luer jake@alogicalparadox.com
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,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.