Can you explain what the JUnit framework for testing in Java is?

JUnit is a popular framework for unit testing in Java. It allows writing and running automated tests to verify the correctness of individual methods and classes.

Main features of JUnit:

• Annotations for marking test methods (@Test), setup methods (@Before, @BeforeEach), and cleanup methods (@After, @AfterEach).
• Asserts for checking expected results (assertEquals, assertTrue, etc.).
• Ability to group tests and run them automatically.

Example of a simple test with JUnit 5:

import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;

class CalculatorTest {
    @Test
    void addition() {
        Calculator calc = new Calculator();
        assertEquals(5, calc.add(2, 3));
    }
}

JUnit helps improve code quality and simplifies the debugging process.