Arrange-Act-Assert pattern in JUnit - Test Execution Trace

Test Overview

This test checks if the Calculator class correctly adds two numbers using the Arrange-Act-Assert pattern. It verifies that the sum of 5 and 3 equals 8.

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() {
        // Arrange
        Calculator calculator = new Calculator();
        int a = 5;
        int b = 3;

        // Act
        int result = calculator.add(a, b);

        // Assert
        assertEquals(8, result, "Sum should be 8");
    }
}

class Calculator {
    public int add(int x, int y) {
        return x + y;
    }
}

Execution Trace - 5 Steps

Step	Action	System State	Assertion	Result
1	Test starts	JUnit test runner initializes CalculatorTest class	-	PASS
2	Arrange: Create Calculator instance and set inputs a=5, b=3	Calculator object created, variables a=5, b=3 assigned	-	PASS
3	Act: Call add method with a and b	Calculator.add(5, 3) called, returns 8	-	PASS
4	Assert: Check if result equals 8	Result is 8	assertEquals(8, result)	PASS
5	Test ends successfully	Test passed with no errors	-	PASS

Failure Scenario

Failing Condition: Calculator.add method returns incorrect sum

Execution Trace Quiz - 3 Questions

What is the purpose of the 'Arrange' step in this test?

A Call the method being tested

B Check the test result

C Set up objects and inputs needed for the test

D Clean up after the test

Key Result

Using the Arrange-Act-Assert pattern helps keep tests clear and organized by separating setup, action, and verification steps.