[spring] Mock MVC - Add Request Parameter to test

I am using spring 3.2 mock mvc to test my controller.My code is

 @Autowired
     private Client client;

     @RequestMapping(value = "/user", method = RequestMethod.GET)
        public String initUserSearchForm(ModelMap modelMap) {
            User user = new User();
            modelMap.addAttribute("User", user);
            return "user";
        }

        @RequestMapping(value = "/byName", method = RequestMethod.GET)
        @ResponseStatus(HttpStatus.OK)
        public
        @ResponseBody
        String getUserByName(
           @RequestParam("firstName") String firstName,
           @RequestParam("lastName") String lastName,
           @ModelAttribute("userClientObject") UserClient userClient) {
            return client.getUserByName(userClient, firstName, lastName);
        }

and I wrote following test:

@Test public void testGetUserByName() throws Exception {
        String firstName = "Jack";
        String lastName = "s";       
        this.userClientObject = client.createClient();
        mockMvc.perform(get("/byName")
                .sessionAttr("userClientObject", this.userClientObject)
                .param("firstName", firstName)
                .param("lastName", lastName)               
        ).andExpect(status().isOk())
                .andExpect(content().contentType("application/json"))
                .andExpect(jsonPath("$[0].id").exists())
                .andExpect(jsonPath("$[0].fn").value("Marge"));
}

what i get is

java.lang.AssertionError: Status expected:<200> but was:<400>
    at org.springframework.test.util.AssertionErrors.fail(AssertionErrors.java:60)
    at org.springframework.test.util.AssertionErrors.assertEquals(AssertionErrors.java:89)
    at org.springframework.test.web.servlet.result.StatusResultMatchers$5.match(StatusResultMatchers.java:546)
    at org.springframework.test.web.servlet.MockMvc$1.andExpect(MockMvc.java:141)

Why this happens? Is it right way to pass the @RequestParam

If anyone came to this question looking for ways to add multiple parameters at the same time (my case), you can use .params with a MultivalueMap instead of adding each .param :

LinkedMultiValueMap<String, String> requestParams = new LinkedMultiValueMap<>()
requestParams.add("id", "1");
requestParams.add("name", "john");
requestParams.add("age", "30");

mockMvc.perform(get("my/endpoint").params(requestParams)).andExpect(status().isOk())

@ModelAttribute is a Spring mapping of request parameters to a particular object type. so your parameters might look like userClient.username and userClient.firstName, etc. as MockMvc imitates a request from a browser, you'll need to pass in the parameters that Spring would use from a form to actually build the UserClient object.

(i think of ModelAttribute is kind of helper to construct an object from a bunch of fields that are going to come in from a form, but you may want to do some reading to get a better definition)