Prog. asisgnments - adding comments, getting local copy with unit tests

My experience is that adding your own comments even within the graded cells is not a problem, as long as you are careful not to accidentally overwrite any of template code. Even adding cells to the notebooks (“Insert → Cell Below”) generally doesn’t cause problems for the graders even when they contain code, as long as you are careful not to redefine any function names that are used in the graded cells. I sometimes add cells with different tests for my code or other “experimental” logic.

There is a topic on the FAQ Thread about this:

Can I add my own cells to a notebook?

Yes, you can use “Insert → Cell Below” to do that. Note that this could confuse the grader in some cases, so the best practice is to add this comment as the first line in any added cells:

# START SKIP FOR GRADING

End of inclusion …

Of course it may be that I have just not explored the full range of this type of addition and there may be other things that will disturb the graders. But you can always test your code again by grading it after your additions. You can submit to the grader as many times as you like and there is no penalty, even if the later submissions fail after you’ve passed the assignment. The system remembers your best scores.