Chương 4: Kiểm thử đơn vị (Unit Test)

Chương này hướng dẫn cách viết unit test cho API trong ứng dụng Java Spring Boot. Nội dung bao gồm cấu trúc test chuẩn, cách mock dependency, kiểm tra validate input, xác thực (authentication/authorization), ghi log, xử lý exception và kiểm tra logic service. Mục tiêu đảm bảo mỗi API hoạt động đúng, an toàn và ổn định trước khi tích hợp hoặc triển khai.

Nội dung chi tiết

 

1. Nguyên tắc Unit Test API

Mỗi API cần test các nhóm case cơ bản:

  1. Validate input

  2. Auth / permission

  3. Business logic

  4. Repository interaction

  5. Exception handling

  6. Logging

  7. HTTP status & response

2. Ví dụ API mẫu

Controller:


@RestController @RequestMapping("/users") @RequiredArgsConstructor public class UserController { private final UserService userService; @PostMapping public ResponseEntity<UserResponse> create( @Valid @RequestBody CreateUserRequest req) { return ResponseEntity.ok(userService.create(req)); } }

DTO:


@Data public class CreateUserRequest { @NotBlank private String username; @Email private String email; }

Service:


@Service @RequiredArgsConstructor public class UserService { private final UserRepository repo; public UserResponse create(CreateUserRequest req) { User u = new User(req.getUsername(), req.getEmail()); repo.save(u); return new UserResponse(u.getId(), u.getUsername()); } }

3. Cấu trúc test chuẩn

Dependency:


<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency>

Controller test dùng:

4. Test Validate Input

Case cần có:


@WebMvcTest(UserController.class) class UserControllerValidationTest { @Autowired private MockMvc mockMvc; @MockBean private UserService userService; @Test void create_shouldFail_whenUsernameBlank() throws Exception { String json = """ {"username":"","email":"a@test.com"} """; mockMvc.perform(post("/users") .contentType(MediaType.APPLICATION_JSON) .content(json)) .andExpect(status().isBadRequest()); } @Test void create_shouldFail_whenEmailInvalid() throws Exception { String json = """ {"username":"john","email":"invalid"} """; mockMvc.perform(post("/users") .contentType(MediaType.APPLICATION_JSON) .content(json)) .andExpect(status().isBadRequest()); } }

5. Test Auth / Permission

Giả sử API cần login:


@WithMockUser @Test void create_shouldSuccess_whenAuthenticated() throws Exception { when(userService.create(any())) .thenReturn(new UserResponse(1L,"john")); String json = """ {"username":"john","email":"a@test.com"} """; mockMvc.perform(post("/users") .contentType(MediaType.APPLICATION_JSON) .content(json)) .andExpect(status().isOk()); }

Test chưa login:


@Test void create_shouldUnauthorized_whenNoAuth() throws Exception { String json = """ {"username":"john","email":"a@test.com"} """; mockMvc.perform(post("/users") .contentType(MediaType.APPLICATION_JSON) .content(json)) .andExpect(status().isUnauthorized()); }

6. Test Business Logic (Service)


@ExtendWith(MockitoExtension.class) class UserServiceTest { @Mock private UserRepository repo; @InjectMocks private UserService service; @Test void create_shouldSaveUser() { CreateUserRequest req = new CreateUserRequest(); req.setUsername("john"); req.setEmail("a@test.com"); when(repo.save(any())).thenAnswer(i -> i.getArgument(0)); UserResponse res = service.create(req); assertEquals("john", res.getUsername()); verify(repo).save(any()); } }

7. Test Exception Handling

Giả sử email trùng:


when(repo.save(any())) .thenThrow(new DataIntegrityViolationException("dup"));

Test:


@Test void create_shouldThrow_whenDuplicateEmail() { CreateUserRequest req = new CreateUserRequest(); req.setUsername("john"); req.setEmail("a@test.com"); when(repo.save(any())) .thenThrow(new RuntimeException("duplicate")); assertThrows(RuntimeException.class, () -> service.create(req)); }

8. Test Logging

Giả sử service có log:


log.info("Create user {}", req.getUsername());

Test log:


@ExtendWith(MockitoExtension.class) class UserServiceLogTest { @Mock private UserRepository repo; @InjectMocks private UserService service; @Test void create_shouldLog() { CreateUserRequest req = new CreateUserRequest(); req.setUsername("john"); req.setEmail("a@test.com"); when(repo.save(any())).thenAnswer(i -> i.getArgument(0)); service.create(req); verify(repo).save(any()); } }

(Thực tế có thể dùng LogCaptor)

9. Test HTTP Response


@Test @WithMockUser void create_shouldReturnBody() throws Exception { when(userService.create(any())) .thenReturn(new UserResponse(1L,"john")); String json = """ {"username":"john","email":"a@test.com"} """; mockMvc.perform(post("/users") .contentType(MediaType.APPLICATION_JSON) .content(json)) .andExpect(status().isOk()) .andExpect(jsonPath("$.username").value("john")); }

10. Danh sách Case chuẩn cho mỗi API

Mỗi API cần tối thiểu:

Validate

Auth

Business

Repository

Exception

Response

Log

 

11. Checklist Unit Test API