TestWatcher for reporting in JUnit - Test Execution Trace

Test Overview

This test uses JUnit's TestWatcher to report test success and failure events. It verifies that the test lifecycle events are logged correctly.

Test Code - JUnit 5

JUnit

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.junit.jupiter.api.extension.TestWatcher;
import org.junit.jupiter.api.extension.ExtensionContext;
import java.util.Optional;

class ReportingTestWatcher implements TestWatcher {
    @Override
    public void testSuccessful(ExtensionContext context) {
        System.out.println("Test succeeded: " + context.getDisplayName());
    }

    @Override
    public void testFailed(ExtensionContext context, Throwable cause) {
        System.out.println("Test failed: " + context.getDisplayName() + ", reason: " + cause.getMessage());
    }

    @Override
    public void testDisabled(ExtensionContext context, Optional<String> reason) {
        System.out.println("Test disabled: " + context.getDisplayName() + ", reason: " + reason.orElse("No reason"));
    }

    @Override
    public void testAborted(ExtensionContext context, Throwable cause) {
        System.out.println("Test aborted: " + context.getDisplayName() + ", reason: " + cause.getMessage());
    }
}

@ExtendWith(ReportingTestWatcher.class)
public class SampleTest {

    @Test
    void testSuccess() {
        // This test will pass
        int sum = 2 + 3;
        org.junit.jupiter.api.Assertions.assertEquals(5, sum);
    }

    @Test
    void testFailure() {
        // This test will fail
        int diff = 5 - 3;
        org.junit.jupiter.api.Assertions.assertEquals(1, diff);
    }
}

Execution Trace - 5 Steps

Step	Action	System State	Assertion	Result
1	Test runner starts and applies ReportingTestWatcher extension	JUnit test environment initialized with TestWatcher extension	-	PASS
2	Runs testSuccess method	Executing testSuccess: calculates sum 2 + 3	Assert sum equals 5	PASS
3	TestWatcher logs success message for testSuccess	Console output: 'Test succeeded: testSuccess()'	Verify success log message printed	PASS
4	Runs testFailure method	Executing testFailure: calculates diff 5 - 3	Assert diff equals 1	FAIL
5	TestWatcher logs failure message for testFailure	Console output: 'Test failed: testFailure(), reason: expected:<1> but was:<2>'	Verify failure log message printed with correct reason	PASS

Failure Scenario

Failing Condition: Assertion in testFailure does not match actual result

Execution Trace Quiz - 3 Questions

What does the TestWatcher do when a test passes?

A Prints 'Test succeeded' with test name

B Throws an exception

C Skips the test

D Does nothing

Key Result

Using TestWatcher helps track and report test lifecycle events clearly, improving test diagnostics and reporting.