@ExtendWith annotation in JUnit - Test Execution Trace

Test Overview

This test uses the @ExtendWith annotation in JUnit 5 to register a custom extension. It verifies that the extension's callback method is called during test execution.

Test Code - JUnit 5

JUnit

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.junit.jupiter.api.extension.BeforeEachCallback;
import org.junit.jupiter.api.extension.ExtensionContext;
import static org.junit.jupiter.api.Assertions.assertTrue;

class MyExtension implements BeforeEachCallback {
    static boolean beforeEachCalled = false;

    @Override
    public void beforeEach(ExtensionContext context) {
        beforeEachCalled = true;
    }
}

@ExtendWith(MyExtension.class)
public class ExtendWithTest {

    @Test
    void testExtensionCalled() {
        assertTrue(MyExtension.beforeEachCalled, "Extension beforeEach should have been called");
    }
}

Execution Trace - 5 Steps

Step	Action	System State	Assertion	Result
1	JUnit test runner starts the test class ExtendWithTest	JUnit framework initialized, test class loaded	-	PASS
2	JUnit detects @ExtendWith(MyExtension.class) and registers MyExtension as an extension	Extension MyExtension is ready to be called before each test	-	PASS
3	JUnit calls MyExtension.beforeEach() before running testExtensionCalled()	MyExtension.beforeEachCalled is set to true	-	PASS
4	JUnit runs testExtensionCalled() method	Test method executing	assertTrue(MyExtension.beforeEachCalled) verifies beforeEachCalled is true	PASS
5	JUnit completes testExtensionCalled() successfully	Test passed	-	PASS

Failure Scenario

Failing Condition: MyExtension.beforeEach() is not called before the test method

Execution Trace Quiz - 3 Questions

What does the @ExtendWith annotation do in this test?

A Marks the test method as disabled

B Registers MyExtension to run before each test method

C Specifies the test method's timeout

D Injects a mock object into the test

Key Result

Use @ExtendWith to add custom behavior before or after tests. Always verify that your extension's callbacks are executed as expected.