How to write Regression Test scripts for Tkinter

[John Roth]

How do I go about writing a unit test or regression test script for
Tkinter? The unittest module only handles non-gui classes.

I'm sure somebody has done it. It has to be possible - Google
found a comment on the [incr Megawidgets] project that they
had borrowed Osterhout's process for doing regression tests, but
I have absolutely no clue as to how he did it, or if it can be
ported to Python.

Any pointers would be appreciated.

John Roth