ActiveRecord tests for patch

Hey folks,

I've got a patch that fixes the problem with erroneous singularization of foreign keys with eager loading (#4117, #6390), and all the AR tests pass. However, I don't yet have a failing test case that can be submitted as a patch (though I can easily reproduce it in an app). Adding a table to the schema seems to require modifying ten different .sql files for all the various supported databases, and I'm not familiar with many of those DDL variants and don't have any way to test that I put the files together correctly since all I run is MySQL. What's a good way to proceed?

Also, The amount of test code I'm going to have to create for this issue is relatively large - five classes, six tables, and at least five test cases. Is that overkill? Is complete coverage on negative tests required here? This situation is particularly gross because it requires using names which have singular forms that can be singularized, but there are very few that give semantically friendly examples and aren't already used in the tests. I could use nonsense names, though that seems aesthetically unpleasing. Or, if someone could advise me how to use custom inflections in AR tests I could go that way.

You can add tables to test/fixtures/db_definitions/schema.rb or AR::
Base.connection.create_table in setup and drop_table in teardown if connection.supports_migrations?

Having to rely on the existing tables does frustrate new tests. Creating new tables and classes on the fly is probably the simplest option, considering the new tables are for these tests in particular.

jeremy