Unit testing in Testing Fundamentals - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple unit test with assertion

What is the result of running this Python unit test code?

Testing Fundamentals

import unittest

def add(a, b):
    return a + b

class TestAdd(unittest.TestCase):
    def test_add_positive(self):
        self.assertEqual(add(2, 3), 5)

if __name__ == '__main__':
    unittest.main(exit=False)

A Test passes with no errors

B Test fails with AssertionError

C SyntaxError due to missing colon

D TypeError because add expects strings

💡 Hint

Check if the add function returns the sum correctly and the assertion matches.

The add function returns the sum of two numbers. The test checks if add(2, 3) equals 5, which is true, so the test passes.

❓ assertion

intermediate

Choosing the correct assertion for checking list length

Which assertion is correct to verify that a list named 'items' has exactly 4 elements in a unit test?

A self.assertIs(items, 4)

B self.assertTrue(items == 4)

C self.assertEqual(len(items), 4)

D self.assertIn(4, items)

💡 Hint

Think about how to check the number of elements in a list.

len(items) returns the number of elements. Using assertEqual compares this number to 4, which is the correct way to check list length.

🔧 Debug

advanced

Identify the error in this unit test code

What error will this Python unittest code raise when run?

Testing Fundamentals

import unittest

def multiply(x, y):
    return x * y

class TestMultiply(unittest.TestCase):
    def test_multiply(self):
        self.assertEqual(multiply(3, 4), 12)
    def test_multiply_fail(self):
        self.assertEqual(multiply(2, 2), 5)

if __name__ == '__main__':
    unittest.main(exit=False)

A TypeError because multiply expects strings

B No error, all tests pass

C SyntaxError due to missing parentheses

D AssertionError in test_multiply_fail

💡 Hint

Check the expected value in the failing assertion.

The test_multiply_fail expects multiply(2, 2) to be 5, but multiply(2, 2) returns 4, causing an AssertionError.

🧠 Conceptual

advanced

Purpose of mocking in unit testing

Why do testers use mocking in unit tests?

A To replace real dependencies with controlled fake objects for isolated testing

B To speed up the program by skipping all function calls

C To automatically generate test cases without writing code

D To convert unit tests into integration tests

💡 Hint

Think about testing parts of code without relying on external systems.

Mocking replaces real parts with fake ones so tests focus on the unit itself without outside influence.

❓ framework

expert

Understanding test discovery in Python unittest

Given this directory structure and files, which command correctly discovers and runs all tests? project/ tests/ test_math.py test_string.py app.py Options:

A python -m unittest run tests

B python -m unittest discover -s tests -p 'test_*.py'

C unittest run tests/

D python app.py --run-tests

💡 Hint

Check the unittest module's discover command syntax.

The unittest module's discover command with -s for start directory and -p for pattern correctly finds test files.