Line and branch coverage in JUnit - Test Execution Trace

Test Overview

This test checks a simple method that returns the maximum of two numbers. It verifies both line coverage and branch coverage by testing different input cases to cover all decision paths.

Test Code - JUnit 5

JUnit

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

class MaxUtil {
    public static int max(int a, int b) {
        if (a > b) {
            return a;
        } else {
            return b;
        }
    }
}

class MaxUtilTest {
    @Test
    public void testMaxFirstGreater() {
        assertEquals(5, MaxUtil.max(5, 3));
    }

    @Test
    public void testMaxSecondGreater() {
        assertEquals(7, MaxUtil.max(4, 7));
    }

    @Test
    public void testMaxEqual() {
        assertEquals(6, MaxUtil.max(6, 6));
    }
}

Execution Trace - 8 Steps

Step	Action	System State	Assertion	Result
1	Test runner starts and loads MaxUtilTest class	JUnit test environment initialized	-	PASS
2	Runs testMaxFirstGreater: calls MaxUtil.max(5, 3)	Inside max method with a=5, b=3	Check if a > b (5 > 3) is true	PASS
3	Returns 5 from max method	max method returns 5	Assert returned value equals 5	PASS
4	Runs testMaxSecondGreater: calls MaxUtil.max(4, 7)	Inside max method with a=4, b=7	Check if a > b (4 > 7) is false	PASS
5	Returns 7 from max method	max method returns 7	Assert returned value equals 7	PASS
6	Runs testMaxEqual: calls MaxUtil.max(6, 6)	Inside max method with a=6, b=6	Check if a > b (6 > 6) is false	PASS
7	Returns 6 from max method	max method returns 6	Assert returned value equals 6	PASS
8	Test runner finishes all tests	All tests executed	All assertions passed	PASS

Failure Scenario

Failing Condition: The max method returns incorrect value for a test case

Execution Trace Quiz - 3 Questions

Which test case covers the branch where 'a > b' is true?

A testMaxSecondGreater

B testMaxEqual

C testMaxFirstGreater

D None of the above

Key Result

To achieve full branch coverage, tests must include cases for all decision outcomes, including equal values when comparing.