I get the feeling that regression testing is used to insure that certain
"dumb bugs" don't appear.

I skimmed a book titled The Craft Of Software Testing: Subsystem Testing
by Brian Marick.  It was interesting, but setting up the tests seemed
like a lot of work.  I could see using it for a device driver or some
small component.  But for a system like pkgsrc or NetBSD, I would need
the computer to help out more.

Ben