Spring Boot - JUnit Error testing MultiPartFile Image Upload RestController with MockMvc - spring

Question

I'm trying to test a controller class that upload an image. The endpoint receives a long Id and a MultipartFile file. The code of the controller is:
#PostMapping(value = "/{userId}/image")
#ResponseStatus(HttpStatus.OK)
public UserDto uploadProfileImage(#PathVariable Long userId, #RequestParam("image") MultipartFile image) throws EntityNotFoundException {
User user = imageService.uploadImage(userId,image);
return UserMapper.makeDto(user);
}
And the test is:
#Test
public void whenUploadingImageThenReturnTheUser()throws Exception{
MockMultipartFile uploadFile = new MockMultipartFile("uploadFile", new byte[1]);
User user = new User("email#mail.com","pass", "name","lastNmae","description","123123",null);
when(imageService.uploadImage(1L,uploadFile)).thenReturn(user);
MvcResult result = mockMvc.perform(MockMvcRequestBuilders.fileUpload("/v1/users/"+1L+"/image").file(uploadFile).accept(contentType)).andExpect(status().isOk()).andReturn();
String content = result.getResponse().getContentAsString();
UserDto userDto =asObject(content);
assertEquals(userDto.getFirstName(),user.getFirstName());
}
When I run the test the console shows:
java.lang.AssertionError: Status
Expected :200
Actual :400
at org.springframework.test.util.AssertionErrors.fail(AssertionErrors.java:54)
at org.springframework.test.util.AssertionErrors.assertEquals(AssertionErrors.java:81)
at org.springframework.test.web.servlet.result.StatusResultMatchers$10.match(StatusResultMatchers.java:665)
at org.springframework.test.web.servlet.MockMvc$1.andExpect(MockMvc.java:171)
at com.empresa.mascotar.userService.controllers.UserControllerTest.whenUploadingImageThenReturnTheUser(UserControllerTest.java:165)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
I don't know why I get a 400 code response.
Could you help me please?
Thanks!