Issue: No indication that the test harness uses a hidden inputvar passed automatically into the student’s function. No guidance provided on not calling the function manually inside your code.
Result: Learners waste time debugging phantom errors and misinterpret the behavior of their logic.
Suggested Fix: refine the exercise description by adding:
“The system automatically calls your function, and the num value automatically receives the following values, 5, then 6, then -2, then SPAM SPAM SPAM. What your code has to do, is calculate the correct outputs for these values; you don't need to worry about feeding the system values."