Integration Testing in Spring Boot

@SpringBootTest
@AutoConfigureMockMvc
public class UserIntegrationTest {
    
    @Autowired
    private MockMvc mockMvc;
    
    @Autowired
    private UserRepository userRepository;
    
    @BeforeEach
    public void setup() {
        userRepository.deleteAll();
    }
    
    @Test
    public void testCreateAndGetUser() throws Exception {
        // Create user via API
        String userJson = "{""name"":""John",""email"":""john@example.com""}";
        
        MvcResult createResult = mockMvc.perform(post("/api/users")
                .contentType(MediaType.APPLICATION_JSON)
                .content(userJson))
                .andExpect(status().isOk())
                .andReturn();
        
        // Extract created user ID
        String response = createResult.getResponse().getContentAsString();
        Long userId = JsonPath.parse(response).read("$.id", Long.class);
        
        // Get user via API
        mockMvc.perform(get("/api/users/" + userId))
                .andExpect(status().isOk())
                .andExpect(jsonPath("$.name", is("John")))
                .andExpect(jsonPath("$.email", is("john@example.com")));
        
        // Verify database directly
        User savedUser = userRepository.findById(userId).orElse(null);
        assertNotNull(savedUser);
        assertEquals("John", savedUser.getName());
    }
}

# application-test.properties
spring.datasource.url=jdbc:h2:mem:testdb
spring.datasource.driverClassName=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=
spring.jpa.database-platform=org.hibernate.dialect.H2Dialect
spring.h2.console.enabled=true

@SpringBootTest
@ActiveProfiles("test")
public class DatabaseIntegrationTest { ... }

@DataJpaTest
public class UserRepositoryTest {
    
    @Autowired
    private TestEntityManager entityManager;
    
    @Autowired
    private UserRepository userRepository;
    
    @Test
    public void testFindByEmail() {
        // Given
        User user = new User("John", "john@example.com");
        entityManager.persist(user);
        entityManager.flush();
        
        // When
        User found = userRepository.findByEmail("john@example.com");
        
        // Then
        assertThat(found.getName()).isEqualTo("John");
    }
}

@RestClientTest(UserClient.class)
public class UserClientTest {
    
    @Autowired
    private UserClient userClient;
    
    @Autowired
    private MockRestServiceServer server;
    
    @Test
    public void testGetUser() {
        server.expect(requestTo("/api/users/1"))
            .andRespond(withSuccess("{""id"":1,""name"":""John""}", MediaType.APPLICATION_JSON));
        
        User user = userClient.getUser(1L);
        assertEquals("John", user.getName());
    }
}

• @SpringBootTest loads full application context for integration testing.
• @AutoConfigureMockMvc enables MockMvc for controller testing.
• Use @DataJpaTest for repository layer tests.
• Use @RestClientTest for REST client tests.
• @ActiveProfiles selects specific configuration for tests.
• Use in-memory database (H2) for faster tests.