I have quick looked many BDD tools and calabash looks right. It is a quite straightforward solution: integrate a http server into iOS project and bridge actions of cucumber step and iOS runtime using accessibility facility. Because predefined steps are quite complete, it is possible just write feature specs in Gherkin without touching ruby code.
But it is always so struggling to ramp up a new open source technology. The first try just failed, even with simplest environment, with a brand new simple view project.
Error message explains itself, I need create this Frameworks group in project to let script continue running. Or it just aborted, no target duplicated, no integration.
The interesting part is, it is an issue known for over 1 year: https://github.com/calabash/calabash-ios/issues/533