Quaff is a Ruby library for writing SIP test scenarios. It is an attempt to create something similar to SIPp (which I also maintain), but which can be more easily integrated into other test suites.
The current version is 0.7.0, and it can be installed as a Ruby gem with 'gem install quaff' (see the RubyGems page for more info). Quaff does not support SDP, but the separate SDP gem can be used to parse SDP bodies.
A set of example Quaff scripts are available here.
This is still an early stage of Quaff's development, and the API is likely to change before the 1.0.0 release. (Hopefully, lots of bugs will be flushed out too - please report any you find on Github.)