Setting up a custom Json Serializer for testing a Spring controller

I am 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 run 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 execute execution in debug mode, I found that an exception was thrown from: com.fasterxml.jackson.databind.ser.std.CollectionSerializer # serializeContents And this is 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 ObjectMapper into my context but it was not used. Another ObjectMapper is used in the Serialization process. This is the ObjectMapper that I am embedding using @Import (HateoasConfiguration.class) into 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;
    }

}