Avoid @MockBean! Use @MockitoBean for Unit Testing in Spring Boot 3.2+

🚀 Introduction: Why is @MockBean Deprecated?

For years, @MockBean has been widely used in Spring Boot unit tests to mock dependencies. However, in Spring Boot 3.2, @MockBean has been deprecated due to performance and maintainability concerns.

🔴 Problems with @MockBean

✔ Creates unnecessary Spring context proxies → Slows down test execution.
✔ Mocks beans globally → Can cause side effects in multiple tests.
✔ Not optimized for Spring Boot 3.2 testing improvements.

✅ Solution: Use @MockitoBean

Spring Boot 3.2 introduces @MockitoBean, which provides:
✔ Faster test execution with direct Mockito integration.
✔ Better isolation of test components.
✔ More reliable unit testing experience.

1️⃣ What is @MockitoBean?

@MockitoBean is a new annotation in Spring Boot 3.2 that acts as a direct replacement for @MockBean.

✔ It creates mock instances for dependencies.
✔ It integrates better with JUnit 5 and Mockito.
✔ It does not require full Spring context reloading.

2️⃣ Replacing @MockBean with @MockitoBean

Let’s take an example where we mock a repository in a service test.

📝 Example 1: Old Approach Using @MockBean (Deprecated)

@SpringBootTest
class UserServiceTest {

    @MockBean  // ❌ Deprecated in Spring Boot 3.2+
    private UserRepository userRepository;

    @Autowired
    private UserService userService;

    @Test
    void testGetUserById() {
        User mockUser = new User(1L, "John Doe");

        Mockito.when(userRepository.findById(1L)).thenReturn(Optional.of(mockUser));

        User result = userService.getUserById(1L);
        assertEquals("John Doe", result.getName());
    }
}

❌ Issues with @MockBean in this approach:

• Requires Spring Context initialization, making tests slower.
• Affects other tests due to global mocking.

✅ Example 2: New Approach Using @MockitoBean (Spring Boot 3.2+)

@SpringBootTest
class UserServiceTest {

    @MockitoBean  // ✅ New Recommended Annotation
    private UserRepository userRepository;

    @Autowired
    private UserService userService;

    @Test
    void testGetUserById() {
        User mockUser = new User(1L, "John Doe");

        Mockito.when(userRepository.findById(1L)).thenReturn(Optional.of(mockUser));

        User result = userService.getUserById(1L);
        assertEquals("John Doe", result.getName());
    }
}

✅ Benefits of using @MockitoBean
✔ Faster execution – Does not reload the Spring Context.
✔ Scoped mocking – Mocks only in the test class.
✔ More stable unit testing experience.

3️⃣ Unit Testing a REST Controller with @MockitoBean and MockMvc

Spring Boot also allows testing REST controllers without starting the full application.

✅ Example: Testing UserController

@WebMvcTest(UserController.class)
class UserControllerTest {

    @Autowired
    private MockMvc mockMvc;

    @MockitoBean  // ✅ Mock only in this test class
    private UserService userService;

    @Test
    void testGetUserById() throws Exception {
        User mockUser = new User(1L, "John Doe");

        Mockito.when(userService.getUserById(1L)).thenReturn(mockUser);

        mockMvc.perform(get("/api/users/1"))
                .andExpect(status().isOk())
                .andExpect(jsonPath("$.name").value("John Doe"));
    }
}

✅ Uses MockMvc to test API endpoints efficiently.
✅ Mocks UserService without loading the full application.

4️⃣ Key Differences: @MockBean vs. @MockitoBean

Feature	@MockBean (Deprecated)	@MockitoBean (Recommended)
Spring Boot Version	Before 3.2	3.2+
Performance	Slower (requires Spring Context)	Faster (Mockito direct integration)
Scope	Global (affects multiple tests)	Local (scoped per test)
Mockito Integration	Uses Spring proxies	Directly integrates with Mockito
Recommended?	❌ No	✅ Yes

🚀 Always use @MockitoBean in Spring Boot 3.2+ for unit tests!

5️⃣ Best Practices for Unit Testing in Spring Boot 3.2+

✔ Use @MockitoBean instead of @MockBean for faster tests.
✔ Use @WebMvcTest for controller testing.
✔ Use @SpringBootTest only for integration tests.
✔ Mock dependencies instead of using real DB connections.
✔ Use Mockito.when() and verify() to validate method calls.

🎯 Conclusion: Why Switch to @MockitoBean?

By switching to @MockitoBean, you get:
✅ Faster test execution (no Spring Context reloads).
✅ Better test isolation (per-test mock scope).
✅ More efficient Mockito integration.

🚀 Are you using @MockitoBean in your Spring Boot 3.2+ projects? Comment below!

🔗 Share this guide with developers to help them migrate from @MockBean to @MockitoBean! 🚀