assertEquals in JUnit - Test Execution Trace

Test Overview

This test checks if the add method of a simple calculator returns the correct sum of two numbers using assertEquals.

Test Code - JUnit 5

JUnit

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

public class CalculatorTest {

    @Test
    public void testAdd() {
        Calculator calc = new Calculator();
        int result = calc.add(2, 3);
        assertEquals(5, result, "2 + 3 should equal 5");
    }
}

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

Execution Trace - 5 Steps

Step	Action	System State	Assertion	Result
1	Test starts	JUnit test runner initializes CalculatorTest	-	PASS
2	Calculator object is created	Calculator instance ready for use	-	PASS
3	Calls add(2, 3) method	Method executes and returns 5	-	PASS
4	assertEquals checks if expected 5 equals actual 5	Comparison of expected and actual values	assertEquals(5, 5)	PASS
5	Test finishes successfully	Test marked as passed in report	-	PASS

Failure Scenario

Failing Condition: The add method returns a wrong sum, e.g., 4 instead of 5

Execution Trace Quiz - 3 Questions

What does assertEquals verify in this test?

A That the method throws an exception

B That the method runs without errors

C That the expected value matches the actual result

D That the object is not null

Key Result

Use assertEquals to compare expected and actual values clearly, providing a helpful message to understand failures.