Which type of testing focuses on the functions of individual software components?

Unit testing is specifically designed to evaluate the functionality of individual components or modules of software in isolation. It verifies that each component behaves as expected and adheres to the specified requirements. By focusing on the smallest testable parts of the application, unit testing allows developers to identify and rectify issues early in the development process, which ultimately leads to better code quality and easier maintenance.

During unit tests, developers write test cases that directly invoke the component's functions with predefined inputs and then check the outputs against expected results. This process ensures that each unit functions correctly in various scenarios, including edge cases. Therefore, unit testing serves as a foundational step before integration and system-level testing, where larger interactions and overall system functionalities are assessed.