shows an example of how you can use unittest in python.
took it from this video: https://www.youtube.com/watch?v=1Lfv5tUGsn8
file 'circles_old.py' shows the old code without changing it. the new one is what the video is about.
to run unittest open command prompt, cd to your directory, then run this command: python -m unittest test_circles OR python -m unittest either way should work.