Why extensions customize JUnit behavior - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to register a JUnit extension using the correct annotation.

JUnit

@[1] MyExtension extension = new MyExtension();

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ARegisterExtension

BExtendWith

CTestExtension

DEnableExtension

Attempts:

3 left

💡 Hint

Common Mistakes

Using @ExtendWith instead of @RegisterExtension for instance fields.

Misspelling the annotation name.

The @RegisterExtension annotation is used to register an extension instance in JUnit 5.

2fill in blank

medium

Complete the code to implement the JUnit extension interface for before each test callback.

JUnit

public class MyExtension implements [1] { }

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AAfterTestExecutionCallback

BBeforeAllCallback

CTestExecutionExceptionHandler

DBeforeEachCallback

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing AfterTestExecutionCallback which runs after tests.

Confusing BeforeAllCallback which runs once before all tests.

The BeforeEachCallback interface allows code to run before each test method.

3fill in blank

hard

Fix the error in the extension method signature to correctly override the beforeEach method.

JUnit

@Override
public void beforeEach([1] context) throws Exception { }

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AExecutionContext

BExtensionContext

CTestContext

DTestInfo

Attempts:

3 left

💡 Hint

Common Mistakes

Using TestContext which is not part of JUnit 5 extension API.

Using TestInfo which is for test methods, not extension callbacks.

The beforeEach method receives an ExtensionContext parameter in JUnit 5 extensions.

4fill in blank

hard

Fill both blanks to implement an extension that prints a message before and after each test.

JUnit

public class MyExtension implements [1], [2] {
  @Override
  public void beforeEach(ExtensionContext context) {
    System.out.println("Starting test");
  }
  @Override
  public void afterEach(ExtensionContext context) {
    System.out.println("Finished test");
  }
}

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ABeforeEachCallback

BAfterAllCallback

CAfterEachCallback

DBeforeAllCallback

Attempts:

3 left

💡 Hint

Common Mistakes

Using AfterAllCallback or BeforeAllCallback which run once per test class, not per test method.

The extension implements BeforeEachCallback and AfterEachCallback to run code before and after each test.

5fill in blank

hard

Fill all three blanks to create a dynamic test factory method using JUnit extension.

JUnit

@TestFactory
Stream<DynamicTest> dynamicTests() {
  return Stream.of("A", "B", "C")
    .map([1] -> DynamicTest.dynamicTest(
      "Test " + [2],
      () -> assertTrue([3].length() > 0)
    ));
}

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Aname

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names inconsistently inside the lambda.

Using 'name' which is not declared as the lambda parameter.

The lambda parameter is value, used to name and test each dynamic test.