What is the relationship between unit testing and debugging?

Unit testing and debugging are interconnected processes that both aim to improve the quality of software, but they serve different purposes within the development lifecycle. Unit testing involves verifying that individual components or units of code function as expected, typically done by the developer during the coding phase. This process involves writing specific tests to check whether each part of the program behaves correctly under a variety of conditions.

When a unit test fails, it indicates that there is a problem with the code, prompting a developer to investigate the issue. This process of investigation often leads to debugging, where the developer identifies the root cause of the failure and corrects it. In this way, unit testing acts as an early detection mechanism for bugs, facilitating debugging by providing clear information about what part of the code is not working properly.

This relationship clarifies why unit testing is considered a form of debugging—since it allows developers to identify bugs in isolated components before the software is integrated or released. Unit tests serve as a proactive approach to prevent bugs, leading to more efficient debugging later in the software development process.