Testing a gem which depends on rails' eviroment

I’ve changed the rails’ inflection file for my project in order to support Spanish pluralize and singularize. I’ve tested it successfully in my rails project.
Now, since it is a common task for me when creating new projects, I want to create a gem for doing this (replace the default inflections file with mine).
The problem is, the gem needs the rails’ environment loaded in order to get tested. How can I do that?
I want to test with rspec.