I have released a second version of my caching logic testing plugin.
It now allows you to test the actions and fragments caching logic. It
works by using a custom fragment store that records what have been
cached or expired.
It also as a new implementation for page cache testing. It now hijack
ActionController::Base caching methods so that they record what has
been cached or expired, so no access to the file system is needed
I also added some unit testing fun.
see  for the release information,  for download and usage
information and  for a direct link to download the plugin
Don't hesitate to comment on my code or to submit bugs. I have no
application making heavy use of fragment and action caching so any
testing of that is appreciated. I'm also not sure the API is the best
one, if you have better idea, please tell me.