When making updates to the spec file at https://github.com/LukeHagar/plex-api-spec, I like to test those changes by generating a Ruby gem and using it in a little Ruby script.
This gist is to document how I perform that testing. You can also check out my first pull request which is the basis for this gist.
First, I edit the /pms/paths/xxx file to add a new response format, etc.