Integration Testing Skill

Purpose

Test component interactions, database operations, and external API integrations using Spring testing framework with TestContainers.

When to Use

• ✅ Testing repository layer with real database

• ✅ Testing REST API endpoints (if applicable)

• ✅ Testing Spring Security configuration

• ✅ Testing external API integrations

Spring Integration Test Patterns

@RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(classes = ApplicationContext.class) @Sql(scripts = "/test-data.sql", executionPhase = Sql.ExecutionPhase.BEFORE_TEST_METHOD) @Sql(scripts = "/cleanup.sql", executionPhase = Sql.ExecutionPhase.AFTER_TEST_METHOD) public class PoliticianIntegrationTest {

@Autowired
private PoliticianRepository repository;

@Test
void shouldCreatePoliticianViaApi() {
    // Arrange
    PoliticianRequest request = new PoliticianRequest("John", "Doe", "S");
    
    // Act
    ResponseEntity<Politician> response = restTemplate.postForEntity(
        "/api/politicians",
        request,
        Politician.class
    );
    
    // Assert
    assertThat(response.getStatusCode()).isEqualTo(HttpStatus.CREATED);
    assertThat(response.getBody()).isNotNull();
    
    // Verify in database
    Politician saved = repository.findById(response.getBody().getId()).orElseThrow();
    assertThat(saved.getFirstName()).isEqualTo("John");
}

}

TestContainers for PostgreSQL

@Testcontainers @RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(classes = ApplicationContext.class) public class DatabaseIntegrationTest {

@ClassRule
public static PostgreSQLContainer<?> postgres = new PostgreSQLContainer<>("postgres:15")
    .withDatabaseName("cia_test")
    .withUsername("test")
    .withPassword("test");

@BeforeClass
public static void setupTestDatabase() {
    System.setProperty("spring.datasource.url", postgres.getJdbcUrl());
    System.setProperty("spring.datasource.username", postgres.getUsername());
    System.setProperty("spring.datasource.password", postgres.getPassword());
}

@Test
public void shouldConnectToDatabase() {
    assertThat(postgres.isRunning()).isTrue();
}

}

Security Integration Tests

@RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(classes = {ApplicationContext.class, SecurityConfig.class}) @WebAppConfiguration public class SecurityIntegrationTest {

@Autowired
private WebApplicationContext context;

private MockMvc mockMvc;

@Before
public void setup() {
    mockMvc = MockMvcBuilders
        .webAppContextSetup(context)
        .apply(springSecurity())
        .build();
}

@Test
@WithMockUser(roles = "ADMIN")
public void shouldAllowAdminAccess() throws Exception {
    mockMvc.perform(get("/api/admin/users"))
        .andExpect(status().isOk());
}

@Test
public void shouldDenyUnauthenticatedAccess() throws Exception {
    mockMvc.perform(get("/api/admin/users"))
        .andExpect(status().isUnauthorized());
}

}

References

• Spring Framework Testing: https://docs.spring.io/spring-framework/reference/testing.html

• TestContainers: https://www.testcontainers.org/