How to get String in response body with mockMvc?

Question

Currently I am testing a @RestController and using the mockMvc to test the endpoint.
I have successfully tested the status but I am unable to validate the response body of the Rest Api.

@Test
public void shouldReturnTheUserDetails() throws Exception {
    mockMvc.perform(get("/api/user")
        .content("{\"name\" : \"testName\"}")
        .andDo(print())
        .andExpect(status().isOk())
        .andExpect(?); // how to validate the  response body
}

The response is

MockHttpServletResponse:
           Status = 202
    Error message = null
          Headers = {Content-Type=[application/json]}
     Content type = application/json
             Body = {"name" : "testName", "age" : 10, "gender" : "M"}
    Forwarded URL = null
   Redirected URL = null
          Cookies = []

How do I validate the response that the name, age and gender are correct?

Answer 1

So multiple ways to do this validate the expected return using mockMVC are -

@Test
public void shouldReturnTheUserDetails() throws Exception {
    var expectedJson = "{\"name\" : \"testName\", \"age\" : 10, \"gender\" : \"M\"}";

    mockMvc.perform(get("/api/user")
        .content("{\"name\" : \"testName\"}")
        .andDo(print())
        .andExpect(status().isOk())
        .andExpect(content().json(expectedJson));
}

Another way is to use the andReturn() and then validate that -

@Test
public void shouldReturnTheUserDetails() throws Exception {
    var expectedJson = "{\"name\" : \"testName\", \"age\" : 10, \"gender\" : \"M\"}";

    MvcResult result = mockMvc.perform(get("/api/user")
        .content("{\"name\" : \"testName\"}")
        .andDo(print())
        .andExpect(status().isOk())
        .andReturn();

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

  Assert.assertEquals(expectedJson, actualJson); // or use any other library for comparison
}