The RB tests take lots of time to run, so I made the SUnit TestRunner
run tests in the background.
I did this using the code - 

runTests
        self runWindow.
       [result _ self suite run.
       WorldState addDeferredUIMessage: [self updateWindow: result. self
beep]] forkAt: Processor userBackgroundPriority.

This was simple, and worked, except that my framerate dropped from the
maximal ~50 to ~1, with update times hovering between 900 and 1500
mSecs.

Any ideas why? I'd expect things running in the background not to affect
my framerate, or at least not beyond some user settable threshold (25
frames/sec).

Daniel