Spring @Valid Annotation Not Functioning

Question

I have a Spring Boot 2.5.3 project and I am attempting to validate some models. However, the tests are returning a 200 status when I am expecting a 4xx error.

Sample endpoint under test:

 @PostMapping("/reports")
 public CAReportDTO addReport(@Valid @RequestBody CAReportDTO caReport) {
     return this.caService.submitForm(caReport);
 }

where CAReportDTO has the following annotations (in part):

public class CAReportDTO {

    private int id;
    @Size(min = 5, max = 7, message 
            = "Employee ID must be between 5 and 7 characters long.")
    @NotNull
    private String empId;
    private int formId;
    private String formTitle;
    @Size(min = 4, max = 5, message 
            = "Work location must be between 4 and 5 characters long.")
    @NotNull
    private String workLocId;
    private CAStatus statusId;
    @NotNull
    @PastOrPresent
    @JsonFormat(pattern = "yyyy-MM-dd")
    private LocalDate incidentDate;

The controller test is as follows (it should fail on both the empId and incidentDate fields):

    @Test
    @WithMockUser(username = "admin", authorities = { RoleConstants.HR.WRK_MNG_CAS })
    public void testAddInvalidReport() throws Exception {
        var dto = new CAReportDTO("test", TEST_ID, "w", LocalDate.now(), "t");
        var jString = mapper.writeValueAsString(dto);

        given(this.caService.submitForm(any(CAReportDTO.class))).willReturn(dto);

        this.mvc.perform(post("/cas/reports").contentType(MediaType.APPLICATION_JSON).content(jString))
                .andExpect(status().is2xxSuccessful());

        dto.setIncidentDate(LocalDate.now().plusMonths(2));
        dto.setEmpId("111111111111111111111111111");
        jString = mapper.writeValueAsString(dto);
        this.mvc.perform(post("/cas/reports").contentType(MediaType.APPLICATION_JSON).content(jString))
                .andExpect(status().is4xxClientError());

    }

The test is failing because the last call returns 200 instead of the expected client error.

I did include org.springframework.boot:spring-boot-starter-validation in my dependencies.

The DTO is actually in a separate library (which is using group: 'org.hibernate.validator:hibernate-validator:7.0.1.Final' for the annotations). Not sure if any version conflicts would cause this?

Thanks!

EDIT: Setup for test class:

@WebMvcTest(CAController.class)
@ActiveProfiles("test")
public class CAControllerTest {

    @Autowired
    private MockMvc mvc;

    @MockBean
    private CAService caService;

    @Autowired
    private ObjectMapper mapper;

    // @Test methods

   }