Project: test a function

Python · Unit 20: Testing and debugging

You are going to write a discount function and the tests that protect it.

The rule: discount(p, pct) returns what you pay, and if pct is not between 0 and 100 the price stays as it was.

def discount(p, pct):
    return p - p * pct / 100

print(discount(200, 10))

Prints

180.0

Exercises in this lesson

You do them in the app, which checks them on the spot and explains why.

1. Complete the code
Complete the test for the impossible percentage.
2. Write the code
Write discount(p, pct): return what you pay after applying the percentage. If pct is below 0 or above 100, return the price unchanged.
3. Write the code
Here are two versions of discount and one has a bug. Complete check(f) so it prints ok when the function respects the rule about the impossible percentage, and fails when it does not. The calls to check are already written.

It opens in your browser. This lesson is part of the full plan; the first unit of each course is free.