How to unit test with @ResponseBody return Json in Spring MVC controller

1. model

public class Dealer {
    private String id;
    private String name;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

2. Controller

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import javax.annotation.Resource;
import java.util.List;

@Controller
@RequestMapping("/dealer")
public class DealerController {
    @Resource(name = "dealerService")
    private DealerService dealerService;

    @RequestMapping("json/all")
    public @ResponseBody List<Dealer> getAllDealers() {
        return dealerService.getAllDealers();
    }
}

3. applicationContext.xml

    
        
    
    
        
           <bean class="org.springframework.web.servlet.view.xml.MarshallingView" p:marshaller-ref="unmarshaller" />
           <bean class="org.springframework.web.servlet.view.json.MappingJacksonJsonView" p:objectMapper-ref="jacksonJsonObjectMapper" />
        
    



    <oxm:class-to-be-bound name="mypackge.Dealer"/>

4. Unit test

import com.google.common.collect.Lists;
import org.apache.http.HttpHeaders;
import org.junit.Before;
import org.junit.Test;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.json.MappingJacksonHttpMessageConverter;
import org.springframework.mock.web.MockHttpServletRequest;
import org.springframework.mock.web.MockHttpServletResponse;
import org.springframework.test.util.ReflectionTestUtils;
import org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter;

import java.util.List;

import static org.junit.Assert.assertEquals;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;

public class TestDealerController {
    private DealerController dealerController;

    @Before
    public void before() throws Exception {
        DealerService dealerService = mock(DealerService.class);
        when(dealerService.getAllDealers()).thenReturn(mockDealers());
        
        dealerController = new DealerController();
        ReflectionTestUtils.setField(dealerController, "dealerService", dealerService);
    }

    @Test
    public void testGetAllDealers() throws Exception {
        MockHttpServletRequest mockRequest = new MockHttpServletRequest();
        mockRequest.setContentType(MediaType.APPLICATION_JSON.toString());
        mockRequest.addHeader(HttpHeaders.ACCEPT, MediaType.APPLICATION_JSON.toString());
        mockRequest.setMethod("GET");
        mockRequest.setRequestURI("/dealer/json/all");

        AnnotationMethodHandlerAdapter handlerAdapter = new AnnotationMethodHandlerAdapter();
        HttpMessageConverter[] messageConverters = {new MappingJacksonHttpMessageConverter()};
        handlerAdapter.setMessageConverters(messageConverters);

        MockHttpServletResponse mockResponse = new MockHttpServletResponse();
        handlerAdapter.handle(mockRequest, mockResponse, dealerController);

        String expected="[{\"id\":\"01\",\"name\":\"dealer-01\"}, {\"id\":\"02\",\"name\":\"dealer-02\"}]";
        assertEquals(expected, mockResponse.getContentAsString());
    }

    private List<Dealer> mockDealers() {
        Dealer dealer01 = new Dealer();
        dealer01.setId("01");
        dealer01.setName("dealer-01");

        Dealer dealer02 = new Dealer();
        dealer02.setId("02");
        dealer02.setName("dealer-02");

        return Lists.newArrayList(dealer01, dealer02);
    }

5. reference
Spring Framework TEST RESTful Web Service (Controller) Offline i.e. No Server, No Database