Summary  
This chapter shows how to use the unittest framework’s assertRaises context manager to verify that code raises specific exceptions (and to check their messages) under error conditions.

General domain of usage  
Unit testing

An **exception** is an event that occurs during program execution that **disrupts the normal flow of instructions**.

Definition

Watch this video to see how to write unit tests that check for exceptions in Python using the unittest framework. You'll learn how to use assertRaises to ensure your code handles errors safely and see practical examples of testing for exceptions in real-world functions.

Testing for exceptions is a crucial part of unit testing because robust code must handle errors gracefully. When you anticipate that certain inputs or situations should trigger an exception, writing tests to confirm this behavior helps you ensure your code fails safely and predictably, rather than crashing unexpectedly or producing incorrect results.

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In the code sample above, `assertRaises` is used to verify that dividing by zero in the `divide` function correctly raises a `ZeroDivisionError`. The test passes only if the exception is raised within the context manager block, confirming that the code responds as expected to invalid input.

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Which assertion is used to check for exceptions in unittest?

Learn how to write reliable Python code by testing it the right way. This short course introduces unit testing using Python’s built-in unittest framework, focusing on practical skills rather than theory. You’ll learn what unit tests are, why they matter, and how to write clear, meaningful tests for real Python functions. The course covers assertions, testing edge cases, handling exceptions, and understanding test failures. You’ll also learn how to structure test files and run tests confidently.

Get started with the basics of unit testing in Python. Learn what unit tests are, why they are important, and how they fit into the software development process.

Learn how to write clear and meaningful unit tests using assertions and by testing a variety of scenarios.

Discover how to test code that raises exceptions and how to interpret test failures.

Learn how to structure your test files and run tests efficiently.

Testing for Exceptions