@ExtendWith annotation in JUnit - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to use the @ExtendWith annotation with MockitoExtension.

JUnit

import org.junit.jupiter.api.extension.ExtendWith;
import org.mockito.junit.jupiter.MockitoExtension;

@ExtendWith([1].class)
public class MyTest {
    // test methods
}

Drag options to blanks, or click blank then click option'

ASpringExtension

BTestExtension

CMockitoExtension

DJUnitExtension

Attempts:

3 left

💡 Hint

Common Mistakes

Using an extension class that does not exist or is unrelated to Mockito.

Forgetting to add .class after the extension name.

The @ExtendWith annotation is used to register extensions in JUnit 5. To enable Mockito support, you use MockitoExtension.class.

2fill in blank

medium

Complete the code to register multiple extensions using @ExtendWith.

JUnit

@ExtendWith([1].class, AnotherExtension.class)
public class MultiExtensionTest {
    // test methods
}

Drag options to blanks, or click blank then click option'

AMockitoExtension

BTestExtension

CJUnitExtension

DSpringExtension

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting .class after the extension name.

Using an extension unrelated to Mockito.

You can register multiple extensions by listing them inside the @ExtendWith annotation. Here, MockitoExtension.class is one of them.

3fill in blank

hard

Fix the error in the @ExtendWith annotation usage.

JUnit

@ExtendWith([1])
public class ErrorTest {
    // test methods
}

Drag options to blanks, or click blank then click option'

AMockitoExtension()

BMockitoExtension

CMockitoExtension.class()

DMockitoExtension.class

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to add .class after the extension name.

Adding parentheses after the class name.

The @ExtendWith annotation requires class literals, so you must use MockitoExtension.class. Omitting .class causes a syntax error.

4fill in blank

hard

Fill both blanks to correctly use @ExtendWith with two extensions.

JUnit

@ExtendWith([1].class, [2].class)
public class CombinedTest {
    // test methods
}

Drag options to blanks, or click blank then click option'

AMockitoExtension

BSpringExtension

CTestExtension

DJUnitExtension

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting .class after extension names.

Using invalid extension names.

You can register multiple extensions by listing their class literals separated by commas inside @ExtendWith. Here, MockitoExtension.class and SpringExtension.class are used.

5fill in blank

hard

Fill all three blanks to create a test class with @ExtendWith registering three extensions.

JUnit

@ExtendWith([1].class, [2].class, [3].class)
public class TripleExtensionTest {
    // test methods
}

Drag options to blanks, or click blank then click option'

AMockitoExtension

BSpringExtension

CTestExtension

DJUnitExtension

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting .class suffix.

Using parentheses after extension names.

You can register multiple extensions by listing their class literals inside @ExtendWith. Here, JUnitExtension.class, SpringExtension.class, and TestExtension.class are used.

Practice

1. What is the primary purpose of the @ExtendWith annotation in JUnit 5?

easy

A. To mark a method as a test case

B. To disable a test method temporarily

C. To register extensions that add extra behavior to tests

D. To specify the order of test execution

Solution

1. Step 1: Understand the role of @ExtendWith

   This annotation is used to register extensions that can add behavior before, after, or around tests.

2. Step 2: Compare with other annotations

   Other annotations like @Test mark test methods, but @ExtendWith is specifically for extensions.

3. Final Answer:

   To register extensions that add extra behavior to tests -> Option C

4. Quick Check:

   @ExtendWith = register extensions [OK]

Hint: Remember: @ExtendWith adds extra test behavior [OK]

Common Mistakes:

• Confusing @ExtendWith with @Test
• Thinking it disables tests
• Assuming it controls test order

2. Which of the following is the correct syntax to use @ExtendWith to register a custom extension named MyExtension.class on a test class?

easy

A. @ExtendWith(MyExtension.class) public class TestClass {}

B. @ExtendWith{MyExtension.class} public class TestClass {}

C. @ExtendWith[MyExtension.class] public class TestClass {}

D. @ExtendWith public class TestClass {}

Solution

1. Step 1: Recall correct annotation syntax

   Annotations use parentheses with class references, like @ExtendWith(MyExtension.class).

2. Step 2: Identify invalid syntax

   Curly braces, square brackets, or angle brackets are not valid for this annotation.

3. Final Answer:

   @ExtendWith(MyExtension.class) public class TestClass {} -> Option A

4. Quick Check:

   Annotation syntax uses parentheses () [OK]

Hint: Use parentheses () with class name for annotations [OK]

Common Mistakes:

• Using curly braces {} instead of parentheses
• Using square brackets [] or angle brackets <>
• Omitting .class after the class name

3. Given the following code snippet, what will be printed when the test runs?

@ExtendWith(MyExtension.class)
public class SampleTest {
    @Test
    void testMethod() {
        System.out.println("Test running");
    }
}

class MyExtension implements BeforeTestExecutionCallback {
    public void beforeTestExecution(ExtensionContext context) {
        System.out.println("Before test");
    }
}

medium

A. Before test

B. Test running\nBefore test

C. Test running

D. Before test\nTest running

Solution

1. Step 1: Understand extension behavior

   The MyExtension implements BeforeTestExecutionCallback, so it runs code before the test method.

2. Step 2: Trace output order

   First, "Before test" prints from the extension, then "Test running" prints from the test method.

3. Final Answer:

   Before test\nTest running -> Option D

4. Quick Check:

   Extension beforeTestExecution runs before test method [OK]

Hint: BeforeTestExecutionCallback runs before test method [OK]

Common Mistakes:

• Assuming extension runs after test
• Ignoring extension output
• Confusing output order

4. Identify the error in the following JUnit 5 test class using @ExtendWith:

@ExtendWith
public class FaultyTest {
    @Test
    void testSomething() {}
}

medium

A. @ExtendWith cannot be used on classes

B. @ExtendWith is missing the extension class argument

C. The test method must be static

D. The test method must return a value

Solution

1. Step 1: Check @ExtendWith usage

   The annotation requires specifying which extension class to use, e.g., @ExtendWith(MyExtension.class).

2. Step 2: Validate other options

   It is valid on classes, test methods do not need to be static or return values.

3. Final Answer:

   @ExtendWith is missing the extension class argument -> Option B

4. Quick Check:

   @ExtendWith needs extension class specified [OK]

Hint: Always specify extension class inside @ExtendWith() [OK]

Common Mistakes:

• Omitting the extension class argument
• Thinking @ExtendWith can't be on classes
• Believing test methods must be static

5. You want to reuse a setup logic that prints "Setup done" before each test method in multiple test classes. How should you apply @ExtendWith to achieve this cleanly?

hard

A. Create a custom extension class implementing BeforeEachCallback and annotate each test class with @ExtendWith(YourExtension.class)

B. Add a static method printing "Setup done" and call it manually in each test method

C. Use @BeforeAll annotation in each test class to print "Setup done"

D. Annotate each test method with @ExtendWith(YourExtension.class) instead of the class

Solution

1. Step 1: Identify reusable setup approach

   Implementing a custom extension with BeforeEachCallback allows running code before each test method.

2. Step 2: Apply @ExtendWith on test classes

   Annotating test classes with @ExtendWith(YourExtension.class) reuses the setup logic cleanly across classes.

3. Step 3: Evaluate other options

   Manually calling methods or using @BeforeAll is less reusable or runs only once per class. Annotating methods individually is repetitive.

4. Final Answer:

   Create a custom extension class implementing BeforeEachCallback and annotate each test class with @ExtendWith(YourExtension.class) -> Option A

5. Quick Check:

   Custom extension + @ExtendWith on class = reusable setup [OK]

Hint: Use custom extension + @ExtendWith on class for reusable setup [OK]

Common Mistakes:

• Calling setup manually in each test
• Using @BeforeAll for per-test setup
• Annotating each test method instead of class