api-spec is a Cucumber extension for testing web APIs. It started from our own collection of Cucumber scenario's for BDDing Nutshell's API updates. Based on a discussion in balanced/balanced-api#431, we decided to see what a gem might look like for packaging up this functionality. It's unclear if there's any value in a specific tool – it's simply just gluing together other gems – but we shall see.
There's currently a fair amount of work, so please refer to the issues for any discussion around the gem's development.