Configuring custom Json Serializer for Spring controller test - spring

Question

I'm testing a controller:
#RestController()
public class MessagesController {
...
}
Using #WebMvcTest annotation:
#RunWith(SpringRunner.class)
#WebMvcTest(value = {MessagesController.class})
public class MessagesControllerTest {
private MockMvc mvc;
....
this.mvc.perform(
get("/messages/{id}", "dummyId")
.contentType(MediaType.APPLICATION_JSON))
.andDo(print())
.andExpect(status().isOk());
...
But when I launch my test Spring tries to serialize an object of type List> and it fails:
Resolved Exception:
Type = org.springframework.http.converter.HttpMessageNotWritableException
ModelAndView:
View name = null
View = null
Model = null
FlashMap:
Attributes = null
MockHttpServletResponse:
Status = 500
Error message = null
Headers = {Content-Type=[application/json;charset=UTF-8]}
Content type = application/json;charset=UTF-8
Body =
Forwarded URL = null
Redirected URL = null
Cookies = []
java.lang.AssertionError: Status
Expected :200
Actual :500
When I follow the execution in debug mode I found that the exception is thrown from : com.fasterxml.jackson.databind.ser.std.CollectionSerializer#serializeContents
And it's a JsonMappingException :
com.fasterxml.jackson.databind.JsonMappingException: Unwrapped property requires use of type information: can not serialize without disabling `SerializationFeature.FAIL_ON_UNWRAPPED_TYPE_IDENTIFIERS` (through reference chain: org.springframework.hateoas.Resource["content"]).
I also tried to inject an ObjectMapper into my context, but it's not used. Another ObjectMapper is used in the Serilaization process. This is the ObjectMapper I inject with #Import(HateoasConfiguration.class) on my test class:
#EnableHypermediaSupport(type = EnableHypermediaSupport.HypermediaType.HAL)
#Configuration
public class HateoasConfiguration
{
private static final String SPRING_HATEOAS_OBJECT_MAPPER = "_halObjectMapper";
#Autowired
#Qualifier(SPRING_HATEOAS_OBJECT_MAPPER)
private ObjectMapper springHateoasObjectMapper;
#Bean(name = "objectMapper")
public ObjectMapper objectMapper() {
springHateoasObjectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
springHateoasObjectMapper.disable(SerializationFeature.FAIL_ON_UNWRAPPED_TYPE_IDENTIFIERS);
springHateoasObjectMapper.registerModules(
new ParameterNamesModule(),
new Jdk8Module(),
new JavaTimeModule(),
new URNModule()
);
return springHateoasObjectMapper;
}
}