Check that we're calling runSuite on an object when prop is not a function.
This caused a bug when running my tests on node-libspotify. I Couldn't track exactly why this function was called with undefined in the first place, but this fixed it and seemed appropriate.
Thanks for this framework by the way :)
Don't call runSuite on just anything, only objects
Check that we're calling runSuite on an object when prop is not a function