[FIXED] In JUnit 5, why are postMethod throwing TransactionSystemException instead return ResponseEntity with bad request?

Issue

I'm pretty new to Spring Boot and JUnit, so im trying to build a Rest API with validation contraints like below:

Entity class:

@Entity
public class CareerLevel {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer careerLevelId;

    @NotNull
    @NotEmpty
    @Size(max = 50)
    private String careerLevel;

    // Getters and Setters
}

Controller:

@PostMapping
public ResponseEntity<CareerLevel> postCareerLevel(@RequestBody @Valid CareerLevel careerLevel) {

    // saving data
    CareerLevel body = careerLevelRepository.save(careerLevel);
    return ResponseEntity.status(201).body(body);
}

When I test post method on Insomnia (or any other HTTP client) with invalid values (null, too long strings, etc) It's returning Bad Request (exactly how I expected). But when I run my Test class, It's throwing an exception called TransactionSystemException

Test Method:

@Test
void testPostCareerLevelInvalidValues() {
    CareerLevel careerLevel = new CareerLevel();
    careerLevel.setCareerLevel("tooLongStriiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiing");

    ResponseEntity<CareerLevel> response1 = controller.postCareerLevel(careerLevel); // throwing TransactionSystemException 
    assertEquals(400, response1.getStatusCode().value());
}

How can I handle that exception and get response data?

Solution

Hi I tried your code locally and added a lombok annotation to create a builder for entity.

see @Builder

I recommend using MockMvc when testing your Controller class.

I also used mockito to mock CareerLevelRepository and injected it into CareerLevelController

@ExtendWith(MockitoExtension.class)
class CareerLevelControllerTest {
    @Mock
    private CareerLevelRepository careerLevelRepository;
    @InjectMocks
    private CareerLevelController careerLevelController;
    private MockMvc mockMvc;

    @BeforeEach
    void setUp() {
        mockMvc = MockMvcBuilders.standaloneSetup(careerLevelController)
                .build();
    }
    private final ObjectMapper objectMapper = new ObjectMapper();

    @Test
    void testPostCareerLevelInvalidValues() throws Exception {
        CareerLevel request = CareerLevel.builder()
                .careerLevel("tooLongStriiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiing")
                .build();

        this.mockMvc
                .perform(post("/career-levels").contentType(MediaType.APPLICATION_JSON)
                        .content(objectMapper.writeValueAsString(request)))
                .andExpect(status().is(400));
    }
}

It simply uses MockMvc to create a request rather than calling the method. ObjectMapper converts our created request to Json which has been sent as body.

Answered By - mbehram
Answer Checked By - Dawn Plyler (JavaFixing Volunteer)