JUnit
JUnit is the most widely used unit testing framework for Java, providing annotations, assertions, and a test runner for writing and executing automated tests. It's the de facto standard that most Java build tools and IDEs support natively, and heavily influenced testing framework design in other languages.
JUnit tests are written as annotated methods (`@Test`) inside a class, using assertion methods (`assertEquals`, `assertTrue`) to check expected outcomes. Its lifecycle annotations (`@BeforeEach`, `@AfterEach`) manage setup and teardown around each test, keeping tests independent of one another.
Beyond pure unit testing, JUnit is also commonly used as the test runner underneath higher-level automation — Selenium and REST-assured tests written in Java are frequently executed and reported through JUnit's runner, even though the tests themselves aren't strictly "unit" tests in the traditional sense.
