Can you integrate MSpec with the MonoDevelop test runner? It's working in Sharp-Develop. Google says 'nothing' so I'm guessing it's not possible as of the current release (2.8.2).
So time passes, and someone has actually created a runner for mspec that works with monodevelop.
MSpecRunner Runner for running Machine.Specifications specs in MonoDevelop
https://github.com/dolittle/MSpecRunner
I've not had time to try it out, but wanted to put it here for completion.