Extension model overview in JUnit - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to register a JUnit 5 extension using the annotation.

JUnit

@ExtendWith([1].class)
public class MyTest {
    @Test
    void testExample() {
        // test code
    }
}

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AJUnitExtension

BTestExtension

CExtension

DMyExtension

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to add .class after the extension name

Using the wrong class name in @ExtendWith

The @ExtendWith annotation requires the class name of the extension to register it. Here, 'MyExtension' is the correct extension class.

2fill in blank

medium

Complete the code to implement the JUnit 5 extension interface for before each test callback.

JUnit

public class MyExtension implements [1] {
    @Override
    public void beforeEach(ExtensionContext context) throws Exception {
        // setup code
    }
}

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ABeforeEachCallback

BTestExecutionExceptionHandler

CBeforeAllCallback

DAfterEachCallback

Attempts:

3 left

💡 Hint

Common Mistakes

Using BeforeAllCallback which runs once before all tests

Confusing AfterEachCallback with BeforeEachCallback

To run code before each test, implement the BeforeEachCallback interface.

3fill in blank

hard

Fix the error in the extension registration code to properly enable the extension.

JUnit

@ExtendWith([1])
public class SampleTest {
    @Test
    void testSomething() {}
}

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AMyExtension.class

BMyExtension

CMyExtension()

Dnew MyExtension()

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting .class after the extension class name

Trying to instantiate the extension inside @ExtendWith

The @ExtendWith annotation requires the class literal with .class, not an instance or just the class name.

4fill in blank

hard

Fill both blanks to create a custom extension that implements both before and after each test callbacks.

JUnit

public class CustomExtension implements [1], [2] {
    @Override
    public void beforeEach(ExtensionContext context) throws Exception {
        // before test
    }

    @Override
    public void afterEach(ExtensionContext context) throws Exception {
        // after test
    }
}

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ABeforeEachCallback

BAfterAllCallback

CAfterEachCallback

DBeforeAllCallback

Attempts:

3 left

💡 Hint

Common Mistakes

Using BeforeAllCallback or AfterAllCallback instead of per-test callbacks

Implementing only one of the two interfaces

To run code before and after each test, implement BeforeEachCallback and AfterEachCallback interfaces.

5fill in blank

hard

Fill all three blanks to create a parameter resolver extension that supports injecting a String parameter with value "Hello".

JUnit

public class StringParameterResolver implements [1] {

    @Override
    public boolean supportsParameter(ParameterContext parameterContext, ExtensionContext extensionContext) throws ParameterResolutionException {
        return parameterContext.getParameter().getType() == [2];
    }

    @Override
    public Object resolveParameter(ParameterContext parameterContext, ExtensionContext extensionContext) throws ParameterResolutionException {
        return [3];
    }
}

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AParameterResolver

BString.class

C"Hello"

DObject.class

Attempts:

3 left

💡 Hint

Common Mistakes

Returning wrong type in supportsParameter check

Not implementing ParameterResolver interface

Returning wrong value in resolveParameter

To create a parameter resolver, implement ParameterResolver. Check if parameter type is String.class and return "Hello" as the resolved value.