Can you explain the difference between MockitoAnnotations and MockitoExtension

MockitoAnnotations

**MockitoAnnotations is a class that allows shorthand creation of objects required for testing. It minimizes repetitive mock creation code and makes the test class more readable. To use Mockito annotations like `@Mock`, `@Spy`, `@Captor`, or `@InjectMocks`, you must call `MockitoAnnotations.initMocks(this)` to initialize these annotated fields. This method was deprecated in Mockito 3 and replaced with `MockitoAnnotations.openMocks(this)`, which returns an `AutoCloseable` instance that should be closed after the test to avoid resource leaks[2][5][7].

Here's an example of using `MockitoAnnotations`:

java
public class ArticleManagerTest extends SampleBaseTestCase {

    @Mock private ArticleCalculator calculator;
    @Mock private ArticleDatabase database;
    @Mock private UserProvider userProvider;

    private ArticleManager manager;

    @Before public void setup() {
        MockitoAnnotations.initMocks(this); // or openMocks(this) in Mockito 3
        manager = new ArticleManager(userProvider, database, calculator);
    }
}

MockitoExtension

**MockitoExtension is a JUnit 5 extension that simplifies the process of using Mockito annotations. By annotating your test class with `@ExtendWith(MockitoExtension.class)`, you can automatically initialize fields annotated with Mockito annotations without needing to manually call `MockitoAnnotations.initMocks(this)` or `MockitoAnnotations.openMocks(this)`. This approach makes the setup more concise and readable[1][3][6].

Here's an example of using `MockitoExtension`:

java
@ExtendWith(MockitoExtension.class)
public class CityServiceImplTest {

    @Mock private CityRepository cityRepository;
    private CityService cityService;

    @BeforeEach
    void setUp() {
        cityService = new CityServiceImpl(cityRepository);
    }

    @Test
    void testService() {
        // Use cityService with mocked cityRepository
    }
}

Key Differences

- Initialization: With MockitoAnnotations, you need to manually call `initMocks()` or `openMocks()` to initialize the mocks. In contrast, MockitoExtension automatically initializes the mocks when used with the `@ExtendWith` annotation.
- JUnit Version Compatibility: MockitoAnnotations can be used in both JUnit 4 and JUnit 5, while MockitoExtension is specifically designed for JUnit 5.
- Code Readability and Conciseness: Using MockitoExtension generally results in cleaner and more concise test code, as it eliminates the need for explicit initialization calls.

In summary, MockitoAnnotations provides a flexible way to initialize mocks that works across different JUnit versions but requires manual initialization. MockitoExtension, on the other hand, offers a more streamlined approach specifically for JUnit 5, automating the initialization process and enhancing code readability.