source: class BookmarkControllerTest {
  
      @Autowired MockMvc mvc;
      @Autowired  @Qualifier("_halObjectMapper") ObjectMapper objectMapper;
  
      @Test
      public void updateABookmarkFailsBecauseDescriptionIsNull() throws Exception {
  
target:         Bookmark input = getSimpleBookmark();
          String location = addBookmark(input);
  
          Resource<Bookmark> output = getBookmark(location);
          output.getContent().setDescription(null);
          mvc.perform(
                  put(output.getId().getHref())
                          .contentType(MediaType.APPLICATION_JSON_UTF8)
                          .accept("application/hal+json;charset=UTF-8", "application/json;charset=UTF-8")
                          .content(objectMapper.writeValueAsString(output.getContent()))
                          .with(csrf())
          ).andDo(print())
                  .andExpect(status().isBadRequest())
                  .andExpect(jsonPath("$[0].field").value("description"));
      }
  
  }