Checking exception type hierarchy in JUnit - Test Execution Trace

Test Overview

This test verifies that a method throws the correct exception type and that the exception is a subclass of the expected exception hierarchy.

Test Code - JUnit 5

JUnit

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

class ExceptionHierarchyTest {

    void methodThatThrows() throws IllegalArgumentException {
        throw new IllegalArgumentException("Invalid argument");
    }

    @Test
    void testExceptionTypeHierarchy() {
        Exception exception = assertThrows(Exception.class, () -> methodThatThrows());
        assertTrue(exception instanceof IllegalArgumentException, "Exception should be IllegalArgumentException");
        assertTrue(exception instanceof RuntimeException, "Exception should be a RuntimeException subclass");
        assertTrue(exception instanceof Exception, "Exception should be an Exception subclass");
    }
}

Execution Trace - 6 Steps

Step	Action	System State	Assertion	Result
1	Test starts	JUnit test runner initialized	-	PASS
2	Calls methodThatThrows() inside assertThrows expecting Exception.class	methodThatThrows() throws IllegalArgumentException	assertThrows captures the thrown IllegalArgumentException as Exception	PASS
3	Checks if caught exception is instance of IllegalArgumentException	exception is IllegalArgumentException	assertTrue passes because exception is IllegalArgumentException	PASS
4	Checks if caught exception is instance of RuntimeException	IllegalArgumentException extends RuntimeException	assertTrue passes because exception is subclass of RuntimeException	PASS
5	Checks if caught exception is instance of Exception	RuntimeException extends Exception	assertTrue passes because exception is subclass of Exception	PASS
6	Test ends successfully	All assertions passed	-	PASS

Failure Scenario

Failing Condition: methodThatThrows() throws a different exception type or no exception

Execution Trace Quiz - 3 Questions

Which assertion confirms the exception is exactly IllegalArgumentException or its subclass?

A assertTrue(exception instanceof IllegalArgumentException)

B assertThrows(Exception.class, ...)

C assertTrue(exception instanceof RuntimeException)

D assertTrue(exception instanceof Exception)

Key Result

Use assertThrows with a broad exception type to catch any subclass, then verify the exact exception type with instanceof checks to confirm the exception hierarchy.