open stepper, make sure it works for (+ 3 4).

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

Make sure that you get a warning when you change the underlying program, and a
warning when the program window disappears.
** closing a tab does not trigger the error message that it should...**

Try stepping backward and forward through programs with correct and erroneous
(syntax errors, runtime errors) executions.
** clicking "end" on a run that ends in an error does not behave correctly ***

Make sure that the step buttons are enabled and disabled as necessary.
... I wish I had a model-checker here.

Try programs which print snips (print-convert-test.ss)


try programs that contain test cases; make sure that the popups behave sensibly.