Testing multiple exceptions in JUnit - Test Execution Trace

Test Overview

This test checks that a method throws the correct exceptions under different error conditions. It verifies that the method throws IllegalArgumentException when input is an empty string, and NullPointerException when input is null.

Test Code - JUnit 5

JUnit

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

public class ExceptionTest {

    public void processInput(String input) {
        if (input == null) {
            throw new NullPointerException("Input cannot be null");
        }
        if (input.isEmpty()) {
            throw new IllegalArgumentException("Input cannot be empty");
        }
    }

    @Test
    public void testProcessInput_throwsIllegalArgumentException() {
        ExceptionTest et = new ExceptionTest();
        assertThrows(IllegalArgumentException.class, () -> et.processInput("") );
    }

    @Test
    public void testProcessInput_throwsNullPointerException() {
        ExceptionTest et = new ExceptionTest();
        assertThrows(NullPointerException.class, () -> et.processInput(null) );
    }
}

Execution Trace - 8 Steps

Step	Action	System State	Assertion	Result
1	Test starts for testProcessInput_throwsIllegalArgumentException	JUnit test runner initialized	-	PASS
2	Calls processInput with empty string ""	Method executes and checks input	-	PASS
3	Throws IllegalArgumentException with message "Input cannot be empty"	Exception thrown as expected	assertThrows verifies IllegalArgumentException is thrown	PASS
4	Test ends for testProcessInput_throwsIllegalArgumentException	Test passed	-	PASS
5	Test starts for testProcessInput_throwsNullPointerException	JUnit test runner ready for next test	-	PASS
6	Calls processInput with null	Method executes and checks input	-	PASS
7	Throws NullPointerException with message "Input cannot be null"	Exception thrown as expected	assertThrows verifies NullPointerException is thrown	PASS
8	Test ends for testProcessInput_throwsNullPointerException	Test passed	-	PASS

Failure Scenario

Failing Condition: Method does not throw the expected exception for given input

Execution Trace Quiz - 3 Questions

What exception is expected when processInput is called with an empty string?

A NullPointerException

B IndexOutOfBoundsException

C IllegalArgumentException

D No exception

Key Result

Always write separate test cases for each expected exception to clearly verify different error conditions.