Cucumber

Validate executable specifications against your code on any modern development stack. With over 40 million downloads, Cucumber Open is the world’s #1 automation tool for Behavior-Driven Development.

https://cucumber.io/

Similar Tools

livingdoc
livingdoc is a Confluence Add-On that allows Behaviour Driven Development. A great benefit is that the test specification follows the "Keyword Driven Development" style.
BDDX
Really simple tool for creating and running BDD tests. It lets anyone create and run BDD tests in bulk automating the whole testing process and simplifying error detection and handling.