Gitnesse is an acceptance testing tool.
It enables a project to store Cucumber feature stories in a git-based wiki, test them against your code, and then update the wiki with the latest test results.
The advantage is, that the features are on a wiki, so non-programmers can see them, and edit using the wiki. Hence an awesome bi-directional testing flow between developers and non-developers on a team.
Conceptually influenced by Fitnesse, thank you Uncle Bob!.
http://gitnesse.com