open stepper, make sure it works for (+ 3 4).  Make sure it only works
for the language levels it's supposed to.  Make sure that you get a
warning when you change the underlying program, and a warning when the
program window disappears. Try stepping backward and forward through
programs with correct and erroneous (syntax errors, runtime errors)
executions.  Make sure that the buttons are enabled and disabled as
necessary.  Try programs which print snips (print-convert-test.ss)

make sure that stepper button appears and disappears as necessary when
language level changes.

try programs that contain test cases. D'Oh!