A variant of how to assert the response body in Spring MVC tests with AssertJ

AssertResponseBodyWithAssertJ.java

  @Autowired private ObjectMapper objectMapper;
  @Autowired private MockMvc mockMvc;

  @Test
  public void create_when_all_is_correct_then_201_Created() throws Exception {

    ResultActions result = mockMvc.perform(post(USERS)
      .contentType(APPLICATION_JSON_UTF8)
      .content(toJson(new UserRequest("user")))
      .accept(APPLICATION_JSON)
    );

    result.andExpect(status().isCreated())
      .andExpect(content().contentType(APPLICATION_JSON_UTF8));
   
    // instead of this:
    result
      .andExpect(jsonPath("$.id", notNullValue()))
      .andExpect(jsonPath("$.name", is("user")));

    // we can do something like this:
    var expected = new UserResponse("user");		
    assertBody(result, expected, "id") // ignore 'id' field
      .satisfies(body -> assertThat(body.getId()).isNotNull()); // and check if it's not null
  }

  private <T> ObjectAssert<T> assertBody(ResultActions result, T expected, String... ignoredFields) throws Exception {
    String body = result.andReturn().getResponse().getContentAsString();
    //noinspection unchecked
    return (ObjectAssert<T>) assertThat(objectMapper.readValue(body, expected.getClass()))
      .isEqualToIgnoringGivenFields(expected, ignoredFields);
  }

  private String toJson(Object object) throws JsonProcessingException {
    return objectMapper.writeValueAsString(object);
  }