How do I run the activerecord unit test suite as part of a dependent gem's test suite?

Hi all,

I think I have found a bug in a gem that extends activerecord (compound_primary_keys). The test case it breaks is already part of the very large and comprehensive suite in the activerecord gem itself. I would like to patch the gem to allow a user to run the standard activerecord unit tests, but with the custom gem loaded as well to verify none of the other original functionality is broken by the gem.

Any straightforward guides on how to do that?