How do I check if a custom plugin works correctly with a new version of Wordpress

Hi

I am working on a few custom plugins-- now one major concern is how to check if a plugin works with a new version of wordpress (as it is released)... Can you let me know how you people(at WPMU Dev) take care of this? Is there some kind of process to follow, to check/verify that a plugin works with a new version of Wordpress? Something that can be programmatically done? I.e. some kind of plugin that basically checks if an existing plugin works correctly with a new version of wordpress? If not programmatically, how do you folks do this? You must face this issue whenever a new version of wordpress is released-- how do you people check if your huge number of plugins work correctly with new releases of wordpress?

Thanks,
Arvind.