I am new to Junit Mockito testcase. I am trying to write REST API controller class .But facing some issue.Can someone please help me on writing the test case.

`@RestController
@RequestMapping(“/storage-connector”)
public class BigQueryController {

private static final Logger logger = LoggerFactory.getLogger(BigQueryController.class);

@Autowired
private BigQueryService bigQueryService;

boolean isSchedulerStarted = false;
//boolean isSchedulerStarted = true;

@PostMapping("/postBigqueryData")
public ResponseEntity<MessageDTO> postDatatoBigquery(@RequestParam("schedular") boolean schedular) throws NoSuchAlgorithmException, KeyManagementException {



  /*  TrustManager[] trustAllCerts = new TrustManager[]
            {new X509TrustManager() {
                public java.security.cert.X509Certificate[] getAcceptedIssuers() {
                    return null;
                }
                public void checkClientTrusted(X509Certificate[] certs, String authType) {
                }
                public void checkServerTrusted(X509Certificate[] certs, String authType) {
                }
            }
            };


    SSLContext sc = SSLContext.getInstance(CommonConstants.SSL);
    sc.init(null, trustAllCerts, new java.security.SecureRandom());
    HttpsURLConnection.setDefaultSSLSocketFactory(sc.getSocketFactory());*/
    MessageDTO result=new MessageDTO();
    if (schedular) {
        isSchedulerStarted = true;
        result=postDatatoBigqueryScheduled();
        if(result.getMessage().equalsIgnoreCase("Success")){
            return ResponseEntity.ok(result);
        }else{
            return ResponseEntity.ok(result);
        }

    } else if (!schedular && isSchedulerStarted) {
        isSchedulerStarted = false;
        result=postDatatoBigqueryScheduled();
        handleSchedulerTime();
        result.setMessage(CommonConstants.SCHEDULAR_STOPPED);
        return ResponseEntity.ok(result);
    }

    return ResponseEntity.ok(result);

}

Also one more test case on

`your t@RestController
@RequestMapping(“/storage-connector”)
public class BigQueryController {

private static final Logger logger = LoggerFactory.getLogger(BigQueryController.class);

@Autowired
private BigQueryService bigQueryService;

boolean isSchedulerStarted = false;
//boolean isSchedulerStarted = true;

@PostMapping("/postBigqueryData")
public ResponseEntity<MessageDTO> postDatatoBigquery(@RequestParam("schedular") boolean schedular) throws NoSuchAlgorithmException, KeyManagementException {



  /*  TrustManager[] trustAllCerts = new TrustManager[]
            {new X509TrustManager() {
                public java.security.cert.X509Certificate[] getAcceptedIssuers() {
                    return null;
                }
                public void checkClientTrusted(X509Certificate[] certs, String authType) {
                }
                public void checkServerTrusted(X509Certificate[] certs, String authType) {
                }
            }
            };


    SSLContext sc = SSLContext.getInstance(CommonConstants.SSL);
    sc.init(null, trustAllCerts, new java.security.SecureRandom());
    HttpsURLConnection.setDefaultSSLSocketFactory(sc.getSocketFactory());*/
    MessageDTO result=new MessageDTO();
    if (schedular) {
        isSchedulerStarted = true;
        result=postDatatoBigqueryScheduled();
        if(result.getMessage().equalsIgnoreCase("Success")){
            return ResponseEntity.ok(result);
        }else{
            return ResponseEntity.ok(result);
        }

    } else if (!schedular && isSchedulerStarted) {
        isSchedulerStarted = false;
        result=postDatatoBigqueryScheduled();
        handleSchedulerTime();
        result.setMessage(CommonConstants.SCHEDULAR_STOPPED);
        return ResponseEntity.ok(result);
    }

    return ResponseEntity.ok(result);

}ext``

your text

I have written like

` @Test
public void testPostDatatoBigquery() throws Exception {
boolean schedular = true;

    MessageDTO messageDTOProxy = new MessageDTO();
    messageDTOProxy.setJobId("e101");
    messageDTOProxy.setMessage("Success");

    when(bigQueryService.postDatatoBigquery()).thenReturn(messageDTOProxy);

    //  when(bigQueryService.postDatatoBigquery().thenReturn(ArgumentMatchers.anyObject());

    ResponseEntity<MessageDTO> messageDTO = bigQueryController.postDatatoBigquery(schedular);
    assertNotNull(messageDTO);

    ///MockMvcRequestBuilders.post("/postBigqueryData").contentType(MediaType.APPLICATION_JSON)

    // assertThat(messageDTO.getStatusCodeValue()).isEqualTo(201);
    ObjectMapper mapper=new ObjectMapper();
    String scheduler1=mapper.writeValueAsString(schedular);

    MockHttpServletRequestBuilder requestBuilder=MockMvcRequestBuilders.post("/postBigqueryData").contentType(MediaType.APPLICATION_JSON)
            .content(scheduler1);

    ResultActions perform=this.mockMvc.perform(requestBuilder);
      MvcResult andReturn= perform.andReturn();
      MockHttpServletResponse response= andReturn.getResponse();
     int status= response.getStatus();
     assertEquals(201,status);
}

`But getting NullPointerException due to getting null in requestBuilder.

MockHttpServletRequestBuilder requestBuilder=MockMvcRequestBuilders.post(“/postBigqueryData”).contentType(MediaType.APPLICATION_JSON)
.content(scheduler1);