Writing tests

Python · Unit 20: Testing and debugging

Full plan
Python
9 exercises

Checking things by hand gets forgotten. If you gather the asserts inside a function whose name starts with test_, you can run them again whenever you want.

It reads like a list of promises: this should give that.

def half(n):
    return n / 2

def test_half():
    assert half(10) == 5
    assert half(0) == 0
    print("half: ok")

test_half()

Prints

half: ok

The rest of the explanation is in the lesson, which is part of the full plan.

Exercises in this lesson

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

1. Predict the output
What does this code print?
2. Put the lines in order
Put the lines in order to write the test for add and run it.
3. Complete the code
Complete the test for the empty case.
4. Multiple choice
You just wrote final_price. What is the best way to test it?
5. Complete the code
Complete the test that checks that 7 is not even.
6. Find the bug
double is written wrong and the check should catch it, but it says everything is fine. Which line has the error?
7. Predict the output
What does this code print?
8. Find the bug
This program defines a test and should run it, but the test is nowhere to be seen in the output. Which line has the error?
9. Predict the output
What does this code print?

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