Test class organization in JUnit - Test Execution Trace

Test Overview

This test class demonstrates how to organize tests using JUnit 5. It includes setup and teardown methods and two simple test methods verifying basic math operations.

Test Code - JUnit 5

JUnit

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

public class CalculatorTest {

    private Calculator calculator;

    @BeforeEach
    void setUp() {
        calculator = new Calculator();
    }

    @AfterEach
    void tearDown() {
        calculator = null;
    }

    @Test
    void testAddition() {
        int result = calculator.add(2, 3);
        assertEquals(5, result, "2 + 3 should equal 5");
    }

    @Test
    void testSubtraction() {
        int result = calculator.subtract(5, 3);
        assertEquals(2, result, "5 - 3 should equal 2");
    }
}

class Calculator {
    int add(int a, int b) {
        return a + b;
    }

    int subtract(int a, int b) {
        return a - b;
    }
}

Execution Trace - 8 Steps

Step	Action	System State	Assertion	Result
1	JUnit starts test run for CalculatorTest class	Test runner initialized, no tests executed yet	-	PASS
2	BeforeEach method setUp() is called to initialize Calculator instance	Calculator instance created and ready for test	-	PASS
3	testAddition() method is executed	Calculator instance available, inputs 2 and 3 provided	assertEquals verifies result is 5	PASS
4	AfterEach method tearDown() is called to clean up Calculator instance	Calculator instance set to null	-	PASS
5	BeforeEach method setUp() is called again before next test	New Calculator instance created for next test	-	PASS
6	testSubtraction() method is executed	Calculator instance available, inputs 5 and 3 provided	assertEquals verifies result is 2	PASS
7	AfterEach method tearDown() is called to clean up Calculator instance	Calculator instance set to null	-	PASS
8	JUnit completes test run for CalculatorTest class	All tests executed successfully	-	PASS

Failure Scenario

Failing Condition: Calculator's add method returns incorrect result

Execution Trace Quiz - 3 Questions

What is the purpose of the @BeforeEach method in this test class?

A To clean up resources after all tests

B To run the test methods

C To create a new Calculator instance before each test

D To assert test results

Key Result

Organizing tests with setup and teardown methods (@BeforeEach and @AfterEach) ensures each test runs independently with a fresh state, preventing interference between tests.