@Mock annotation in JUnit - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the @Mock annotation in JUnit testing?

The @Mock annotation is used to create mock objects. These are fake versions of real objects that simulate behavior for testing without using the actual implementation.

intermediate

How do you initialize mocks annotated with @Mock in a JUnit 5 test class?

You initialize mocks by calling MockitoAnnotations.openMocks(this) in a setup method annotated with @BeforeEach. This prepares the mock objects before each test runs.

intermediate

What is the difference between a mock and a spy in testing?

A mock simulates an object and does not call real methods unless specified. A spy wraps a real object and calls real methods unless stubbed to do otherwise.

beginner

Can you use @Mock without a mocking framework like Mockito?

No, @Mock is part of Mockito and requires it to create mock objects. Without Mockito or a similar framework, @Mock has no effect.

beginner

Why is mocking useful in unit testing?

Mocking helps isolate the unit being tested by replacing dependencies with controlled fake objects. This makes tests faster, more reliable, and focused on the unit's behavior.

What does the @Mock annotation do in a JUnit test?

A Marks a test method to be ignored

B Runs the actual method implementation

C Initializes the test class

D Creates a fake object to simulate behavior

@Mock creates a fake object to simulate behavior for testing.

How do you activate mocks annotated with @Mock in JUnit 5?

A Use <code>@RunWith(MockitoJUnitRunner.class)</code>

B Call <code>MockitoAnnotations.openMocks(this)</code> in <code>@BeforeEach</code>

C Mocks are active by default

D Call <code>initMocks()</code> in <code>@AfterEach</code>

In JUnit 5, you activate mocks by calling MockitoAnnotations.openMocks(this) in a setup method.

Which framework provides the @Mock annotation?

A TestNG

B JUnit

C Mockito

D Selenium

@Mock is provided by the Mockito framework.

What is a key benefit of using mocks in unit tests?

A Isolates the unit by replacing dependencies

B Runs tests slower

C Requires real database connections

D Makes tests dependent on network

Mocks isolate the unit by replacing dependencies with controlled fake objects.

Which statement about mocks is true?

A Mocks simulate objects without calling real methods by default

B Mocks always call real methods

C Mocks cannot be used in JUnit tests

D Mocks are used to style UI components

Mocks simulate objects and do not call real methods unless specified.

Explain how the @Mock annotation works and why it is useful in unit testing.

Think about replacing real parts with fake ones to test only what you want.

Describe the steps to use @Mock in a JUnit 5 test class.

Initialization is key before running tests.