unit test Spring MissingServletRequestParameterException JSON response

Question

I have POST method in a Spring boot rest controller as follows

@RequestMapping(value="/post/action/bookmark", method=RequestMethod.POST)
public @ResponseBody Map<String, String> bookmarkPost(
        @RequestParam(value="actionType",required=true) String actionType,
        @RequestParam(value="postId",required=true) String postId,
        @CurrentUser User user) throws Exception{
    return service.bookmarkPost(postId, actionType, user);
}

now if I test with missing parameter in Postman I get an 400 http response and a JSON body:

{
  "timestamp": "2015-07-20",
  "status": 400,
  "error": "Bad Request",
  "exception": "org.springframework.web.bind.MissingServletRequestParameterException",
  "message": "Required String parameter 'actionType' is not present",
  "path": "/post/action/bookmark"
}

until now it's OK, but when I try to unit test I don't get the JSON response back

@Test
public void bookmarkMissingActionTypeParam() throws Exception{
    // @formatter:off
    mockMvc.perform(
                post("/post/action/bookmark")
                    .accept(MediaType.APPLICATION_JSON)
                    .param("postId", "55ab8831036437e96e8250b6")
                    )
            .andExpect(status().isBadRequest())
            .andExpect(jsonPath("$.exception", containsString("MissingServletRequestParameterException")));
    // @formatter:on
}

the test fails and produces

java.lang.IllegalArgumentException: json can not be null or empty

I did a .andDo(print()) and found that there is no body in the response

MockHttpServletResponse:
          Status = 400
   Error message = Required String parameter 'actionType' is not present
         Headers = {X-Content-Type-Options=[nosniff], X-XSS-Protection=[1; mode=block], Cache-Control=[no-cache, no-store], Pragma=[no-cache], Expires=[1], X-Frame-Options=[DENY]}
    Content type = null
            Body = 
   Forwarded URL = null
  Redirected URL = null
         Cookies = []

why am I not getting the JSON response while unit testing my controller, but do receive it in manual testing using Postman or cUrl?

EDIT: I've added @WebIntegrationTest but got the same error:

import static org.hamcrest.Matchers.containsString;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
import static org.springframework.test.web.servlet.result.MockMvcResultHandlers.print;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.SpringApplicationConfiguration;
import org.springframework.boot.test.WebIntegrationTest;
import org.springframework.http.MediaType;
import org.springframework.security.web.FilterChainProxy;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.web.servlet.MockMvc;
import org.springframework.test.web.servlet.setup.MockMvcBuilders;
import org.springframework.web.context.WebApplicationContext;

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = RestApplication.class)
@WebIntegrationTest
public class PostControllerTest {

    private MockMvc mockMvc;

    @Autowired
    private WebApplicationContext webApplicationContext;

    @Autowired
    private FilterChainProxy springSecurityFilterChain;

    @Before
    public void setUp() {
        mockMvc = MockMvcBuilders.webAppContextSetup(webApplicationContext)
                .addFilter(springSecurityFilterChain)
                .build();
    }  

    @Test
    public void bookmarkMissingActionTypeParam() throws Exception{
        // @formatter:off
        mockMvc.perform(
                    post("/post/action/bookmark")
                        .accept(MediaType.APPLICATION_JSON)
                        .param("postId", "55ab8831036437e96e8250b6")
                        )
                .andDo(print())
                .andExpect(status().isBadRequest())
                .andExpect(jsonPath("$.exception", containsString("MissingServletRequestParameterException")));
        // @formatter:on
    }
}

Answer 1

This is because Spring Boot has auto-configured an exception handler org.springframework.boot.autoconfigure.web.BasicErrorController which is probably not present in your unit tests. A way to get it will be to use the Spring Boot testing support related annotations:

@SpringApplicationConfiguration
@WebIntegrationTest

More details are here

Update: You are absolutely right, the behavior is very different in UI vs in test, the error pages which respond to status codes are not correctly hooked up in a non-servlet test environment. Improving this behavior can be a good bug to open for Spring MVC and/or Spring Boot.

For now, I have a workaround which simulates the behavior of BasicErrorController the following way:

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = {RestApplication.class, TestConfiguration.class})
@WebIntegrationTest
public class PostControllerTest {

    private MockMvc mockMvc;

    @Autowired
    private WebApplicationContext webApplicationContext;

    @Autowired
    private FilterChainProxy springSecurityFilterChain;

    @Before
    public void setUp() {
        mockMvc = MockMvcBuilders.webAppContextSetup(webApplicationContext)
                .addFilter(springSecurityFilterChain)
                .build();
    }  

    @Test
    public void bookmarkMissingActionTypeParam() throws Exception{
        // @formatter:off
        mockMvc.perform(
                    post("/post/action/bookmark")
                        .accept(MediaType.APPLICATION_JSON)
                        .param("postId", "55ab8831036437e96e8250b6")
                        )
                .andDo(print())
                .andExpect(status().isBadRequest())
                .andExpect(jsonPath("$.exception", containsString("MissingServletRequestParameterException")));
        // @formatter:on
    }
}
     @Configuration
    public static class TestConfiguration {


        @Bean
        public ErrorController errorController(ErrorAttributes errorAttributes) {
            return new ErrorController(errorAttributes);
        }
    }
@ControllerAdvice
class ErrorController extends BasicErrorController {

    public ErrorController(ErrorAttributes errorAttributes) {
        super(errorAttributes);
    }

    @Override
    @ExceptionHandler(Exception.class)
    @ResponseBody
    public ResponseEntity<Map<String, Object>> error(HttpServletRequest request) {
        return super.error(request);
    }
}

What I am doing here is adding a ControllerAdvice which handles the Exception flow and delegates back to the BasicErrorController. This would atleast make the behavior consistent for you.

Answer 2

Originally, it should fix the error by @ResponseBody tag when defining your REST controller method. it will fix json error in the test class. But, as you are using spring boot, you will define the controller class with @RestController and it should automatically take care of the error without defining @Controller and @ResponseType tags.