If you are running ferret as a Drb server you may encounter problems while trying to run your test or specs. This issue happens because when you start the ferret server with ruby script/ferret_start it faults to production environment.
You you should not have this problem if the production and test environments are set to the same port numbers in config/ferret_server.yml
If you prefer to have different port numbers (which is what I advise), make sure you start the ferret server for the test environment as well.
RAILS_ENV=test script/ferret_start
Hope that helps.