This lesson's interactive features are locked, please to keep using them
Unit Tests
If you end up working as a programmer, you'll spend a lot of time writing your own unit tests. So far we've provided unit tests for you, but it's useful to know how they work.
When you're doing your own testing, you'll usually use a library for writing and running tests. For example, in Python, pytest and unittest are quite popular.
But it's also OK to write tests from scratch sometimes. We do that on Boot.dev so that the tests integrate nicely with our online environment. That's what the main_test.py file is: a custom test harness that we've written for each of your lessons.
Assignment
Let's flip the script: in main.py you'll find a read-only, almost correct function called avg_luck_boost. It's used in Fantasy Quest to calculate the average "luck" boost granted to a party of players when they defeat a boss, to determine the loot that they receive.
The function can be used like this:
luck_boosts: list[int] = [5, 3, 10]
avg_boost: float = avg_luck_boost(luck_boosts)
print(avg_boost) # 6.0
Run the tests. Notice that they all pass! But there's a problem... some odd behavior isn't covered by the existing test cases.
What happens if no party member has a luck boost? The function will try to divide by zero, i.e. the length of the input list, and crash the program.
luck_boosts: list[int] = []
avg_boost: float = avg_luck_boost(luck_boosts) # ZeroDivisionError
What we want this function to do if the input list is empty is to return 0.0. Add a test case to the list in test_cases.py to check for this behavior.
Don't worry, this test is meant to fail! We'll be fixing the function in the next lesson.