spring-testing

name	spring-testing
description	Spring Boot testing with @SpringBootTest, MockMvc, and Testcontainers

Spring Boot Testing Patterns

Reliable tests for Spring Boot services and APIs. Prefer slice tests for speed, full context when needed.

Selective Reading Rule

Read only files relevant to the request. Use the content map to focus.

Content Map

File	Description	When to Read
slice-tests.md	@WebMvcTest, @DataJpaTest	Fast feedback
integration.md	@SpringBootTest, Testcontainers	Real dependencies
mockmvc.md	MockMvc usage	Controller tests
test-data.md	Test fixtures, builders	Clean data setup

Core Patterns

1. Web Slice Tests

@WebMvcTest(UserController.class)
class UserControllerTest {

    @Autowired
    private MockMvc mockMvc;

    @MockBean
    private UserService userService;

    @Test
    void getUser_returnsUser() throws Exception {
        when(userService.findById("u1"))
            .thenReturn(Optional.of(new User("u1", "[e-mail]")));

        mockMvc.perform(get("/api/v1/users/u1"))
            .andExpect(status().isOk())
            .andExpect(jsonPath("$.email").value("[e-mail]"));
    }
}

2. Data JPA Slice

@DataJpaTest
class UserRepositoryTest {

    @Autowired
    private UserRepository userRepository;

    @Test
    void findByEmail_returnsUser() {
        var user = userRepository.save(new User("u1", "[e-mail]"));
        assertThat(userRepository.findByEmail("[e-mail]")).isPresent();
    }
}

3. Full Integration Test

@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
@Testcontainers
class UserControllerIT {

    @Container
    static PostgreSQLContainer<?> postgres = new PostgreSQLContainer<>("postgres:15");

    @Autowired
    private TestRestTemplate restTemplate;

    @Test
    void createUser_returnsCreated() {
        var request = new CreateUserRequest("[e-mail]", "Dev");
        var response = restTemplate.postForEntity("/api/v1/users", request, UserResponse.class);
        assertThat(response.getStatusCode()).isEqualTo(HttpStatus.CREATED);
    }
}

Decision Checklist

• Slice test for controller/repo?
• Use MockMvc over full context?
• Testcontainers for real DB?
• Avoid shared state between tests?

Anti-Patterns

Anti-Pattern	Why Bad	Better Approach
@SpringBootTest for all tests	Slow	Slice tests
Real DB without isolation	Flaky	Testcontainers
Static mutable fixtures	Hidden coupling	Builders/per-test setup

Related Skills

Need	Skill
Core Spring patterns	@[skills/spring-boot-patterns]
Data access	@[skills/spring-data-jpa]