WebMvcConfigurationSupport override makes ModelAndView null in MockMVC test

Question

While trying to get my PUT MockMvc test to work, I found that JSON was not supported. Using an answer from this thread: Configure MappingJacksonHttpMessageConverter

I was able to resolve this by extending the WebMvcConfigurationSupport class. However, when I use this override, it appears as though the ModelAndView data returned in my GET tests is now NULL. I know I can get the response data using this:

String content = result.getResponse().getContentAsString();

But, does anyone have an explanation for why the ModelAndView data is NULL?

Here is my MockMVC test class:

@RunWith(SpringJUnit4ClassRunner.class)
@WebAppConfiguration
@ContextConfiguration("test-rest-context.xml")
public class AccountControllerTest {


@Autowired
private WebApplicationContext webApplicationContext;

private MockMvc mockMvc;

private MediaType contentType = new MediaType(MediaType.APPLICATION_JSON.getType(),
        MediaType.APPLICATION_JSON.getSubtype(),
        Charset.forName("utf8"));

@Before
public void setUp() throws Exception {
    this.mockMvc = MockMvcBuilders.webAppContextSetup(this.webApplicationContext).build();
}

@Test
public void findCustomerByID() throws Exception {
    MvcResult result = mockMvc.perform(get("/api/account/customers/{customerID}", "123").accept(contentType)
            .param("fields", "id", "email", "userName")
            .contentType(contentType))
            .andExpect(status().isOk())
            .andReturn();

    ModelAndView mav = result.getModelAndView();
    // mav is NULL here after I extend WebMvcConfigurationSupport class.

}    
}