Mockito dependency setup in JUnit - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add the Mockito dependency in Maven's <dependencies> section.

JUnit

<dependency>
    <groupId>org.mockito</groupId>
    <artifactId>mockito-core</artifactId>
    <version>[1]</version>
    <scope>test</scope>
</dependency>

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

A3.12.4

B4.11.0

C2.23.4

D5.0.0

Attempts:

3 left

💡 Hint

Common Mistakes

Using an outdated or too new version that might not be compatible with your JUnit version.

A stable Mockito version for JUnit testing is 3.12.4. Using this version ensures compatibility and stability.

2fill in blank

medium

Complete the Gradle dependency line to include Mockito for testing.

JUnit

testImplementation '[1]:mockito-core:3.12.4'

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

Amockito

Borg.junit.jupiter

Cjunit

Dorg.mockito

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'junit' or 'mockito' alone as group ID, which is incorrect.

The group ID for Mockito in Gradle is 'org.mockito'. This is required to fetch the correct library.

3fill in blank

hard

Fix the error in the Mockito annotation import statement.

JUnit

import org.mockito.[1];

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AMock

Bmock

CMocks

Dmockito

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase 'mock' which does not exist as an annotation.

The correct annotation to create mock objects is '@Mock' with capital 'M'. The import must be 'org.mockito.Mock'.

4fill in blank

hard

Fill both blanks to initialize Mockito annotations in a JUnit 4 test class.

JUnit

@Before
public void setup() {
    Mockito.[1](this);
    // other setup code
}

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AAnnotations

BinitMocks

Cinitialize

DsetupMocks

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-existent methods like 'Annotations' or 'initialize'.

In JUnit 4, Mockito annotations are initialized by calling Mockito.initMocks(this) inside a method annotated with @Before.

5fill in blank

hard

Fill all three blanks to use MockitoExtension with JUnit 5.

JUnit

@ExtendWith([1].class)
public class MyTest {

    @Mock
    private Service service;

    @BeforeEach
    void init() {
        MockitoAnnotations.[2](this);
    }

    @Test
    void testService() {
        when(service.call()).thenReturn([3]);
        // test code
    }
}

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

AMockitoExtension

BopenMocks

C"mocked response"

DinitMocks

Attempts:

3 left

💡 Hint

Common Mistakes

Using initMocks instead of openMocks in JUnit 5.

Not providing a valid return value in when().

JUnit 5 uses @ExtendWith(MockitoExtension.class) to enable Mockito. The method openMocks(this) initializes mocks. The when() method needs a return value, here a string "mocked response".

Practice

1. What is the main purpose of setting up Mockito as a dependency in a JUnit project?

easy

A. To automatically generate user interfaces

B. To create fake objects for testing without using real implementations

C. To improve the performance of the application in production

D. To deploy the application to a server

Solution

1. Step 1: Understand Mockito's role

   Mockito is a tool used to create mock objects that simulate real objects in tests.

2. Step 2: Identify the purpose in testing

   Using mocks helps isolate the code under test by replacing dependencies with fake versions.

3. Final Answer:

   To create fake objects for testing without using real implementations -> Option B

4. Quick Check:

   Mockito = mock objects for testing [OK]

Hint: Mockito creates fake objects to test code easily [OK]

Common Mistakes:

• Thinking Mockito improves production performance
• Confusing Mockito with UI tools
• Assuming Mockito deploys applications

2. Which of the following is the correct Maven dependency snippet to add Mockito version 4.11.0 for test scope?

easy

A.
org.mockito
mockito-core
4.11.0
test

B.
org.mockito
mockito-core
4.11.0

C.
org.mockito
mockito-all
3.0.0
compile

D.
org.mockito
mockito-core
5.0.0
test

Solution

1. Step 1: Check groupId and artifactId

   The correct groupId is 'org.mockito' and artifactId is 'mockito-core' for Mockito library.

2. Step 2: Verify version and scope

   Version 4.11.0 is correct and scope should be 'test' to use Mockito only during testing.

3. Final Answer:

   Correct Maven dependency with version 4.11.0 and test scope -> Option A

4. Quick Check:

   Maven dependency with test scope = org.mockito mockito-core 4.11.0 test [OK]

Hint: Use 'mockito-core' with test scope and correct version [OK]

Common Mistakes:

• Omitting the test scope
• Using wrong artifactId like 'mockito-all'
• Using incorrect or too new version

3. You want to use Mockito in a JUnit 5 project with Gradle. Which of the following Gradle dependency setups correctly adds Mockito version 4.11.0 only for test implementation?

easy

A. testImplementation 'org.mockito:mockito-core:4.11.0'

B. implementation 'org.mockito:mockito-core:4.11.0'

C. compileOnly 'org.mockito:mockito-core:4.11.0'

D. runtimeOnly 'org.mockito:mockito-core:4.11.0'

Solution

1. Step 1: Understand Gradle scopes

   testImplementation means the dependency is available only during test compilation and runtime.

2. Step 2: Choose correct scope for Mockito

   Mockito is used only in tests, so testImplementation is the correct scope.

3. Final Answer:

   testImplementation 'org.mockito:mockito-core:4.11.0' -> Option A

4. Quick Check:

   Mockito test dependency = testImplementation [OK]

Hint: Use testImplementation for test-only dependencies in Gradle [OK]

Common Mistakes:

• Using implementation instead of testImplementation
• Using compileOnly which excludes runtime
• Using runtimeOnly which excludes compile time

4. Given the following JUnit test code snippet using Mockito, what will be the output of System.out.println(mockService.getData());?

import static org.mockito.Mockito.*;

public class ServiceTest {
  @Test
  void testGetData() {
    DataService mockService = mock(DataService.class);
    when(mockService.getData()).thenReturn("Mocked Data");
    System.out.println(mockService.getData());
  }
}

medium

A. Original data from DataService

B. null

C. Throws NullPointerException

D. Mocked Data

Solution

1. Step 1: Understand mock behavior

   The mock object returns what is specified in when().thenReturn(), here "Mocked Data".

2. Step 2: Check the printed output

   Calling getData() on mockService returns "Mocked Data", so it prints that string.

3. Final Answer:

   Mocked Data -> Option D

4. Quick Check:

   Mockito when().thenReturn() sets output = Mocked Data [OK]

Hint: when().thenReturn() sets mock method output [OK]

Common Mistakes:

• Expecting null because it's a mock
• Assuming real method runs
• Thinking it throws an exception

5. Identify the error in the following Mockito setup code snippet:

import static org.mockito.Mockito.*;

public class UserServiceTest {
  @Mock
  UserRepository repo;

  @Test
  void testUser() {
    when(repo.findUser()).thenReturn(new User("Alice"));
    UserService service = new UserService(repo);
    assertEquals("Alice", service.getUserName());
  }
}

medium

A. Incorrect method name findUser() should be getUser()

B. UserService constructor should not accept repo

C. Missing MockitoAnnotations.openMocks(this) to initialize @Mock fields

D. assertEquals parameters are reversed

Solution

1. Step 1: Check @Mock initialization

   @Mock fields need initialization, usually by calling MockitoAnnotations.openMocks(this) in setup.

2. Step 2: Verify test setup completeness

   Without initialization, repo remains null causing NullPointerException when used.

3. Final Answer:

   Missing MockitoAnnotations.openMocks(this) to initialize @Mock fields -> Option C

4. Quick Check:

   @Mock requires initialization = Missing MockitoAnnotations.openMocks(this) to initialize @Mock fields [OK]

Hint: Always initialize @Mock with MockitoAnnotations.openMocks(this) [OK]

Common Mistakes:

• Forgetting to initialize @Mock fields
• Assuming @Mock works without setup
• Mixing method names without checking