A unit test is a software testing method where individual components or functions of a program are tested in isolation. The goal is to ensure that each part of the code behaves as expected, helping to identify bugs early in the development process. Unit tests are typically automated, allowing developers to run them frequently and efficiently. These tests are usually written by the same developers who create the code, using frameworks like JUnit for Java or pytest for Python. By validating small sections of code, unit tests contribute to higher code quality and make it easier to maintain and refactor software over time.