Difference between @Before, @BeforeClass, @BeforeEach, and @BeforeAll annotations in JUnit

In JUnit, there are several annotations used for setting up test cases. These annotations help in executing certain methods before running the actual test methods. Here is a brief explanation of the differences between @Before, @BeforeClass, @BeforeEach, and @BeforeAll annotations:

• @Before: This annotation is used to mark a method that should be executed before each test method in the test class. It is suitable for setting up common test data or resources needed for each test method.
• @BeforeClass: This annotation is used to mark a method that should be executed once before any of the test methods in the test class. It is typically used for static setup activities that are needed only once.
• @BeforeEach: Introduced in JUnit 5, this annotation is used to mark a method that should be executed before each test method, similar to @Before in JUnit 4. It provides a more descriptive alternative to @Before.
• @BeforeAll: Introduced in JUnit 5, this annotation is used to mark a method that should be executed once before any of the test methods in the test class, similar to @BeforeClass in JUnit 4. It provides a more descriptive alternative to @BeforeClass.

By understanding the differences between these annotations, you can effectively manage the setup activities in your JUnit test classes and ensure proper initialization before running test methods.