Unit testing is a software testing technique that focuses on verifying the functionality of the smallest testable parts of an application, such as functions, methods, or classes. These individual components, referred to as "units," are tested in isolation to ensure they work as expected. Unit testing is a key part of the Test-Driven Development (TDD) process and is typically performed by developers during the early stages of the software development lifecycle.

Key Features of Unit Testing

Unit tests are designed to validate specific behaviors of a unit by providing input values and verifying the output against expected results. They are independent of external systems like databases or APIs, often using mock objects or stubs to simulate dependencies.

For example, a unit test for a calculator's add method might check if adding 5 and 3 returns 8. This ensures the logic of the method is correct without relying on other parts of the application.

Example of Unit Testing in Python