TestWatcher for reporting in JUnit - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is TestWatcher in JUnit?

TestWatcher is a JUnit extension that allows you to add custom behavior when tests succeed, fail, or are skipped. It helps in reporting and logging test results.

beginner

How do you use TestWatcher to log a message when a test fails?

Override the <code>failed(Throwable e, Description description)</code> method in a TestWatcher subclass to add custom logging or reporting when a test fails.

beginner

Which method in TestWatcher is called when a test succeeds?

The succeeded(Description description) method is called when a test passes successfully.

intermediate

Why use TestWatcher instead of @After or @Before methods for reporting?

TestWatcher provides hooks specifically for test result events (success, failure, skip), making it easier and cleaner to add reporting logic tied directly to test outcomes.

intermediate

Show a simple example of a TestWatcher that prints test start and finish messages.

import org.junit.rules.TestWatcher;
import org.junit.runner.Description;

public class MyTestWatcher extends TestWatcher {
  @Override
  protected void starting(Description description) {
    System.out.println("Starting: " + description.getMethodName());
  }
  @Override
  protected void finished(Description description) {
    System.out.println("Finished: " + description.getMethodName());
  }
}

Which TestWatcher method is called when a test fails?

A succeeded(Description description)

B finished(Description description)

C starting(Description description)

D failed(Throwable e, Description description)

The failed method is triggered when a test fails, allowing custom actions like logging or reporting.

What is the main purpose of using TestWatcher in JUnit?

A To add custom behavior on test lifecycle events

B To write test assertions

C To configure test timeouts

D To create test data

TestWatcher lets you add custom actions when tests start, succeed, fail, or finish.

Which method would you override to log when a test starts?

A starting(Description description)

B failed(Throwable e, Description description)

C succeeded(Description description)

D finished(Description description)

The starting method is called before a test begins.

Can TestWatcher be used to skip tests?

A Only for parameterized tests

B No, it only observes test events

C Only if combined with @Ignore

D Yes, it can skip tests

TestWatcher observes test events but does not control test execution or skipping.

Which JUnit version introduced TestWatcher as an extension?

A JUnit 5

B JUnit 3

C JUnit 4

D JUnit 6

TestWatcher was introduced in JUnit 4 as a Rule for test lifecycle event handling.

Explain how TestWatcher helps improve test reporting in JUnit.

Think about how you can react to test outcomes automatically.

Describe how to implement a TestWatcher that logs test start and failure events.

Focus on which methods to override and what to log.