Extension model overview in JUnit - Test Execution Trace

Test Overview

This test demonstrates how to use JUnit 5 extension model to log test execution start and end. It verifies that the extension methods are called during the test lifecycle.

Test Code - JUnit 5

JUnit

import org.junit.jupiter.api.extension.*;
import org.junit.jupiter.api.*;

class LoggingExtension implements BeforeTestExecutionCallback, AfterTestExecutionCallback {
    @Override
    public void beforeTestExecution(ExtensionContext context) {
        System.out.println("Starting test: " + context.getDisplayName());
    }

    @Override
    public void afterTestExecution(ExtensionContext context) {
        System.out.println("Finished test: " + context.getDisplayName());
    }
}

@ExtendWith(LoggingExtension.class)
public class ExtensionModelTest {

    @Test
    void sampleTest() {
        Assertions.assertTrue(1 + 1 == 2);
    }
}

Execution Trace - 6 Steps

Step	Action	System State	Assertion	Result
1	JUnit test runner starts the test suite	JUnit framework initialized, test class ExtensionModelTest loaded	-	PASS
2	JUnit detects @ExtendWith annotation and registers LoggingExtension	LoggingExtension instance ready to intercept test lifecycle events	-	PASS
3	JUnit calls LoggingExtension.beforeTestExecution before sampleTest runs	Console prints: "Starting test: sampleTest()"	Verify beforeTestExecution callback is invoked	PASS
4	JUnit executes sampleTest method	Test method runs, assertion 1 + 1 == 2 evaluated	AssertTrue passes as 1 + 1 equals 2	PASS
5	JUnit calls LoggingExtension.afterTestExecution after sampleTest completes	Console prints: "Finished test: sampleTest()"	Verify afterTestExecution callback is invoked	PASS
6	JUnit test runner completes the test suite	Test report generated showing sampleTest passed	Test result is PASS	PASS

Failure Scenario

Failing Condition: If the LoggingExtension is not registered or its methods throw exceptions

Execution Trace Quiz - 3 Questions

What does the LoggingExtension.beforeTestExecution method do in this test?

A Prints a message before the test method runs

B Runs the test assertion

C Prints a message after the test method runs

D Skips the test method

Key Result

Using JUnit 5 extensions allows you to add custom behavior before and after tests, improving test reporting and setup without changing test code.