Backend Testing

Functionality required by the "Pflichtenheft" must be tested.

Spring Boot Controller Testing

Scope

We only test at the controller layer, verifying the correct HTTP behavior, request/response mapping, validation, and controller-service interaction. (→ Blackbox-Testing)
No mocking of the controller, but mocking/stubbing of lower layers (e.g., services or repositories) is allowed when needed.

Default Tools

1. Spring Boot Test ( @SpringBootTest) – for full application context tests (optional, slower).
2. @WebMvcTest – for isolated controller tests (recommended for speed and focus).
3. MockMvc – to simulate HTTP requests to the controller.
4. Mockito – for mocking services under the controller.
5. AssertJ / Hamcrest – for fluent assertions.
6. JUnit 5 – as default test engine.

Testing Approach

• Use @WebMvcTest(YourController.class) to load only the web layer.
• Inject MockMvc to perform requests.
• Mock external services (e.g., service layer beans) with @MockBean.
• Cover at least:
  • Request mapping
  • Validation rules
  • Expected response codes and JSON bodies

Example Controller Test

Let's say we have this simple controller:

@RestController
@RequestMapping("/api/users")
public class UserController {
    private final UserService userService;
    public UserController(UserService userService) {
        this.userService = userService;
    }

    @GetMapping("/{id}")
    public ResponseEntity<UserDto> getUser(@PathVariable Long id) {
        return ResponseEntity.ok(userService.getUserById(id));
    }
}

Here’s a corresponding controller test: (this file should lay inside src/test/java/com/agilesoftwareengineering/[your-application]/UserControllerTest.class)

@WebMvcTest(UserController.class)
class UserControllerTest {

    @Autowired
    private MockMvc mockMvc;

    @MockBean
    private UserService userService;

    @Test
    void shouldReturnUserById() throws Exception {
        UserDto user = new UserDto(1L, "Alice");
        Mockito.when(userService.getUserById(1L)).thenReturn(user);

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

Notes

• Stick to controller-only logic (i.e., no testing service/repo logic here).
• Run these tests on every merge or pull request.
• Consider using Testcontainers if you eventually expand to integration testing (e.g., testing DB + controller together).