Lars Wirzenius and Daniel Silverstone announce the Fable project.

given all stakeholders need to understand acceptance criteria
when Fable is used to document them
then all stakeholders understand them
and they can be automatically tested

Fable is a tool set for documenting acceptance criteria for a system, in a way that's understandable by all stakeholders, and for implementing automated tests to verify the criteria are being met.

See the Fable home page, including links to source code and Debian packages. There is a tutorial (PDF), examples, and documentation. Fable is free software, but doesn't constrain the license of the generated documentation or test programs.