Fitnesse (https://fitnesse.org) is an open-source testing framework that enables software developers and testers to collaboratively write and maintain test cases. Fitnesse is particularly notable for its use in acceptance test-driven development (ATDD) and its straightforward wiki-powered interface that allows users to write tests in a simple and readable format. It integrates well with different programming languages and environments, making it a versatile choice for automated testing. Fitnesse is designed to simplify the process of creating and executing comprehensive test suites, and its user-friendly approach helps teams to define, understand, and execute acceptance tests efficiently.