What tools or approaches do you use when writing tests?

When writing tests in Java, I usually use the following tools and approaches:

• JUnit — the main framework for unit testing. It allows writing tests, using annotations (@Test, @Before, @After), and checking results with assertions.
• Mockito — for creating mock objects and simulating dependency behavior.
• AssertJ or Hamcrest — for more expressive and readable assertions.
• TestNG — an alternative framework with extended capabilities, such as test parameterization.

Approaches:

• Write independent, isolated tests.
• Use the AAA principle (Arrange, Act, Assert).
• Cover both positive and negative scenarios.
• Write tests that are easy to maintain and read.

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 additionTest() {
        Calculator calc = new Calculator();
        assertEquals(5, calc.add(2, 3));
    }
}