Chai is an assertion library for Node.js and browser-based JavaScript applications. It functions as both a behavior-driven development and test-driven development framework, providing a system to verify code outputs, application state, and general logic.
The project is an extensible validation engine that uses a plugin-based system to allow the registration of custom assertions and specialized data checks. It supports multiple modular assertion styles to accommodate different validation philosophies.
The library covers a broad range of data validation capabilities, including the inspection of deep object properties via dot-notation, the verification of collection membership, and the validation of object keys and property descriptors. It also includes tools for monitoring value changes and configuring assertion error formatting.
