Week 4, First programming assignment does not grade my work

Interesting! I tried making the same mistake that you did, so that I could understand the behavior and file a bug about it. But what I found is that in my case the test cases in the notebook do fail in exactly the way that you’d hope:

So I believe this says that you have an out of date version of the notebook and the test cases. Unfortunately, the test cases are in a separate file, so the procedure to update to the latest version is a little complicated. You need to click “File → Open” and then delete all the “dot py” files, in particular public_tests.py and test_utils.py, rename your notebook and then click “Help → Lab Help → Get Latest Version” as described on the FAQ Thread. Once the refresh completes, you’ll then need to copy/paste your completed code from your saved copy of the notebook to the new one.