How to test Rest Controller with static util invocation using JUnit and Mockito

I have Rest Controller with the method create(validation using util class + databaseService(databaseDao + caching))

@RestController
@RequestMapping("files")
public class FilesController {
    private IDbFilesDao dbFilesService;
    private Map<String, Table> tables;

    public FilesController(IDbFilesDao dbFilesService, Map<String, Table> tables) {
        this.dbFilesService = dbFilesService;
        this.tables = tables;
    }

    @PostMapping("{table}")
    public ResponseEntity createTable(@PathVariable("table") String tableName,
                                         @RequestBody File file) {
        FilesValidator.validateAdding(tableName, tables, file);

        dbFilesService.create(tableName, file);

        URI location = ServletUriComponentsBuilder.fromCurrentRequest().buildAndExpand(file.getKey()).toUri();
        return ResponseEntity.created(location).build();
    }
}

I have a Test:

@RunWith(SpringRunner.class)
@WebMvcTest(value = FilesController.class, secure = false)
public class FilesControllerTest {
    @Autowired
    private MockMvc mockMvc;

    @MockBean
    private IDbFilesDao dbFilesService;

    @MockBean
    private Map<String, Table> tables;

    @Test
    public void create() throws Exception {
        RequestBuilder requestBuilder = MockMvcRequestBuilders
                .post("/files/tableName")
                .accept(MediaType.APPLICATION_JSON)
                .content(POST_JSON_BODY)
                .contentType(MediaType.APPLICATION_JSON);
        MvcResult result = mockMvc.perform(requestBuilder).andReturn();
        MockHttpServletResponse response = result.getResponse();
        assertEquals(HttpStatus.CREATED.value(), response.getStatus());
    }
}

It works well only without this row in @RestContoller:

FilesValidator.validateAdding(tableName, tables, file);

With this row - 404 not found.

FilesValidator - util class with static methods. It checks if data is valid and do nothing or throw a Runtime Exception with statuc code ( 404 for example).

How can I fix it without deliting Validation?