Summary
This chapter covers unit testing by implementing small tests for individual functions or classes to validate their behavior and catch errors early.

General domain of usage
Software development

Unit testing is a **foundational practice** in sustaining code quality in Python. Unit testing involves writing small tests that check individual pieces of your code—typically functions or classes—to ensure they behave as expected. The main goal is to catch errors early, before they can propagate and cause more complex problems in your application. By running these tests regularly, you can confidently make changes to your code, knowing that existing functionality will not break unexpectedly.

A basic unit test usually involves:

- Setting up some input;
- Calling the function under test;
- Asserting that the output matches what you expect.

This process not only helps you find bugs but also clarifies how your code is supposed to work, acting as **living documentation** for your project.

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

# Simple test using assert statement
result = add(2, 3)
assert result == 5, f"Expected 5 but got {result}"

# If the assertion passes, nothing happens.
# If it fails, an AssertionError is raised.

Why are tests important for code quality?

Master the principles of writing clean, maintainable, and efficient Python code. Learn to identify code smells, apply refactoring techniques, and adopt best practices for code quality. Practice your skills with hands-on tasks designed for those familiar with basic Python syntax.

Explore the fundamental concepts of code quality, why it matters, and how to recognize poor code in Python.

Delve into practical refactoring methods to enhance Python code structure and eliminate code smells.

Adopt Pythonic conventions and idioms to write elegant, efficient, and maintainable code.

Learn strategies for maintaining code quality over time, including documentation, testing, and code reviews.

Testing for Quality

1. Why are tests important for code quality?

2. What are the benefits of writing tests?