Rails - Jul 2005 - rake clone_structure_to_test doesn't clone structure properly

For my development database, I created a field and made it not null,
then later on I decided the field should be allowed to be null.  Now
as I change my db and run rake clone_structure_to_test so that I can
run unit tests, it always makes that field not null, and I get at on
of errors when I run the tests.  So I have to go in and change it so
the field can be null, and everything''s fine.

How do I make it copy the exact structure over?  Thanks