Which automated testing tool is often used for unit testing in Java?

JUnit is a widely used framework specifically designed for unit testing in Java applications. It provides a structured way to write and run tests for individual pieces of code, typically methods within classes. JUnit allows developers to create test cases that can verify the correctness of their code by checking expected results against actual outcomes.

It supports annotations like @Test, @Before, and @After, which help organize tests and manage setup and teardown operations. Its integration with build tools like Maven and Gradle makes it easy to run tests as part of a continuous integration process. Furthermore, JUnit's simplicity and robust community support have made it the standard for unit testing in Java environments.

In contrast, other options serve different purposes. TestNG is a testing framework similar to JUnit but more focused on integration testing and providing advanced features such as parallel test execution and data-driven testing. Mockito is a framework used for mocking in unit tests to simulate the behavior of complex objects. Selenium is primarily a tool for automated browser testing rather than unit testing.