QUnit is a powerful, easy-to-use JavaScript testing framework that is widely used for testing code in web applications. It is particularly known for its capability to test both client-side and server-side JavaScript, making it a versatile tool for developers. QUnit offers features such as assertion utilities, test lifecycle management, and extensibility via plugins, ensuring comprehensive test coverage. Developed by the jQuery team, QUnit is well-documented and has a supportive community, facilitating smooth integration into various JavaScript projects.