one of the important tools in the eco-center of software development and issue tracking is test case management.
Tools such as TestLink, TestMaster, Mercury TestDirector provide a database with the relevant functionality.
Integration to the issue tracker provides a link between tests and the issues they created, are blocked on, etc.
JIRA should have a generic integration to such tools, and specific easy integration to 1 or 2 leading tools.
Best would be if JIRA can provide such a database on its own. Its not a rocket science field, and integrated support can be very interesting.
see http://rndmgmttrenches.blogspot.com/2005/08/building-test-case-management-solution.html for my take on the issue.