assertNotEquals in JUnit - Test Execution Trace

Test Overview

This test checks that two strings are not equal using assertNotEquals in JUnit. It verifies that the actual output differs from an incorrect expected value.

Test Code - JUnit 5

JUnit

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

public class NotEqualsTest {
    @Test
    public void testStringsAreNotEqual() {
        String actual = "Hello World";
        String wrongExpected = "Hello Jupiter";
        assertNotEquals(wrongExpected, actual, "Strings should not be equal");
    }
}

Execution Trace - 6 Steps

Step	Action	System State	Assertion	Result
1	Test starts	JUnit test runner initialized	-	PASS
2	Runs testStringsAreNotEqual method	Method execution begins	-	PASS
3	Assigns actual = "Hello World"	Variable actual holds "Hello World"	-	PASS
4	Assigns wrongExpected = "Hello Jupiter"	Variable wrongExpected holds "Hello Jupiter"	-	PASS
5	Calls assertNotEquals(wrongExpected, actual, "Strings should not be equal")	Comparing "Hello Jupiter" and "Hello World"	Verify that wrongExpected != actual	PASS
6	Test completes successfully	No exceptions thrown	-	PASS

Failure Scenario

Failing Condition: If actual and wrongExpected strings are equal

Execution Trace Quiz - 3 Questions

What does assertNotEquals verify in this test?

A That the actual string is null

B That the two strings are the same

C That the two strings are different

D That the expected string is empty

Key Result

Use assertNotEquals to confirm two values are different, helping catch unexpected equality bugs.