@Mock vs. @InjectMocks in Mockito: What\'s the Difference?

Understanding the Distinction Between @Mock and @InjectMocks in Mockito

Mockito, a renowned mocking framework in Java, provides two annotations, @Mock and @InjectMocks, to facilitate unit testing. While they both play crucial roles in the testing process, they have distinct functionalities.

@Mock: The Mock Creation Tool

The @Mock annotation is used to create mock objects. A mock object is a lightweight substitute for a real object that simulates its behavior in a controlled manner. When you annotate a class or interface with @Mock, Mockito generates a mock implementation that can be manipulated and verified during unit tests.

@InjectMocks: The Dependency Injection Facilitator

In contrast to @Mock, @InjectMocks serves a different purpose. It is applied to the class under test to inject mocks or spies (instances of the real class that can be partially mocked) that have been created using the @Mock annotation. This injection process takes place automatically during test initialization, making it convenient to set up test configurations.

How They Work Together

To demonstrate the interplay between @Mock and @InjectMocks, consider the following code snippet:

@RunWith(MockitoJUnitRunner.class)
public class SomeManagerTest {

    @InjectMocks
    private SomeManager someManager;

    @Mock
    private SomeDependency someDependency; // injected into someManager

    // tests...

}

In this example, the @InjectMocks annotation is applied to the SomeManagerTest class, specifying that it is the class under test. The @Mock annotation is used to create a mock for the SomeDependency class. When the test is run, the mock dependency is injected into the someManager instance.

By combining @Mock and @InjectMocks, we can streamline the mock setup process and simplify the testing of complex class interactions. It is important to note that the MockitoJUnitRunner.class (or MockitoExtension.class for JUnit 5) must be included in the test class or initialized manually to initialize the mocks and inject them.

The above is the detailed content of @Mock vs. @InjectMocks in Mockito: What\'s the Difference?. For more information, please follow other related articles on the PHP Chinese website!