How to check String in response body with mockMvc

Question

I have simple integration test

@Test
public void shouldReturnErrorMessageToAdminWhenCreatingUserWithUsedUserName() throws Exception {
    mockMvc.perform(post("/api/users").header("Authorization", base64ForTestUser).contentType(MediaType.APPLICATION_JSON)
        .content("{\"userName\":\"testUserDetails\",\"firstName\":\"xxx\",\"lastName\":\"xxx\",\"password\":\"xxx\"}"))
        .andDo(print())
        .andExpect(status().isBadRequest())
        .andExpect(?);
}

In last line I want to compare string received in response body to expected string

And in response I get:

MockHttpServletResponse:
          Status = 400
   Error message = null
         Headers = {Content-Type=[application/json]}
    Content type = application/json
            Body = "Username already taken"
   Forwarded URL = null
  Redirected URL = null

Tried some tricks with content(), body() but nothing worked.

Answer 1

You can call andReturn() and use the returned MvcResult object to get the content as a String.

See below:

MvcResult result = mockMvc.perform(post("/api/users").header("Authorization", base64ForTestUser).contentType(MediaType.APPLICATION_JSON)
            .content("{\"userName\":\"testUserDetails\",\"firstName\":\"xxx\",\"lastName\":\"xxx\",\"password\":\"xxx\"}"))
            .andDo(MockMvcResultHandlers.print())
            .andExpect(status().isBadRequest())
            .andReturn();

String content = result.getResponse().getContentAsString();
// do what you will