Hi friends 
Plz help me out in writing test class for the below class 




public class EF_UpdateOKTA
{
    public EF_UpdateOKTA()
    {
        UpdateEFKotaQueue();
    }
    public void UpdateEFKotaQueue()
    {
        List<string> lstEF_OKTA_QueueID = new List<string>();
        /*string strQuery =  EF_SOQL_Statements__c.getValues('EF_OKTA_Queue_Batch_Query').Type__c + ' ' + EF_SOQL_Statements__c.getValues('EF_OKTA_Queue_Batch_Query').Fields__c +
                           EF_SOQL_Statements__c.getValues('EF_OKTA_Queue_Batch_Query').Relationship_fields__c + ' from ' +  EF_SOQL_Statements__c.getValues('EF_OKTA_Queue_Batch_Query').Object__c +
                           ' where ' + EF_SOQL_Statements__c.getValues('EF_OKTA_Queue_Batch_Query').Filter__c;
        system.debug('strQuery strQuery strQuery ::' + strQuery );
        List <EF_OKTA_Queue__c> lstEFOKTA_Queue_QueryData = Database.Query(strQuery);*/
       
        List <EF_OKTA_Queue__c> lstEFOKTA_Queue_QueryData = [SELECT Id, status__c, EF_Requested_Resource__c, OKTA_JSON__c,OKTA_Response__c, number_tried__c, EF_Requested_Resource__r.EF_Resource_Metadata__r.OKTA_App_ID__c, EF_Requested_Resource__r.EF_Request_ID__r.User_Name__r.Okta_Id__c, EF_Requested_Resource__r.Request_Type__c from EF_OKTA_Queue__c where status__c='Request Sent' and number_tried__c<10 limit 10];
        system.debug('lstEFOKTA_Queue_QueryDatalstEFOKTA_Queue_QueryData::' + lstEFOKTA_Queue_QueryData);
        
        for(EF_OKTA_Queue__c objEF_OKTA_Queue_Local : lstEFOKTA_Queue_QueryData)
        {
            lstEF_OKTA_QueueID.add(objEF_OKTA_Queue_Local.Id);
        }
       
        if(lstEF_OKTA_QueueID.size()>0)
        {
            list<EF_OKTA_Queue__c> lstEfOKtatoUpdate = new list<EF_OKTA_Queue__c>();
            for(EF_OKTA_Queue__c oQueue: [select id, EF_Requested_Resource__r.EF_Request_ID__r.Okta_Id__c,
                            EF_Requested_Resource__r.EF_Request_ID__r.User_Name__r.Okta_Id__c,
                            OKTA_JSON__c, number_tried__c, EF_Requested_Resource__r.Request_Type__c,
                            EF_Requested_Resource__r.EF_Resource_Metadata__r.OKTA_App_ID__c, Status__c
                            from EF_OKTA_Queue__c
                            where id in : lstEF_OKTA_QueueID])
            {
                string userID = oQueue.EF_Requested_Resource__r.EF_Request_ID__r.Okta_Id__c!=''?
                                oQueue.EF_Requested_Resource__r.EF_Request_ID__r.Okta_Id__c:oQueue.EF_Requested_Resource__r.EF_Request_ID__r.User_Name__r.Okta_Id__c;

                string appID = oQueue.EF_Requested_Resource__r.EF_Resource_Metadata__r.OKTA_App_ID__c;
               
                string strURLEnd = OKTA_EndPoint__c.getValues('OKTA').Site_URL__c;
                strURLEnd = strURLEnd + '/apps/' + appID + '/users/' + userID;
               
                String result     = '[]';
                String authToken    = OKTA_EndPoint__c.getValues('OKTA').Auth_token__c;
                Http h = new Http();
                HttpRequest req   = new HttpRequest();
                req.setEndpoint(strURLEnd);
                req.setMethod('GET');
                req.setHeader('Accept', 'application/json');
                req.setHeader('Authorization', authToken);
               
                HttpResponse res = h.send(req);
               
                if (200 == res.getStatusCode())
                {
                    result = res.getBody();
                    map<string, Object> mapDataToUpdate = (map<string, Object>)JSON.deserializeUntyped(result);
                   
                    if(mapDataToUpdate.get('status') == 'Completed')
                    {
                        oQueue.Status__c = 'Complete';
                        lstEfOktatoUpdate.add(oQueue);
                    }
                }
            }
           
            if(lstEfOKtatoUpdate.size()>0)
            {
                try{update lstEfOKtatoUpdate;}
                catch(Exception ex){EF_Error_Log.logException('EF_OKTA_Queue', lstEfOKtatoUpdate, 'DML', 'HIGH', ex.getMessage());
                }
            }
        }
    }


}





=====================================================================
I am struggling with the Error  test fail 


@isTest
private class EF_UpdateOKTA_Test {


    //There are three A's(Arrange, Act, Assert) that you'll need to take care of in your test class

     static testMethod void testCallout() {
      
        /* Populate Test data, in your case in EF_abc_Queue__c object and other parent object where the data is being pulled up by the SOQL you
        have in actuall class satisfying the WHERE condition(where status__c='Request Sent' and number_tried__c<10)
        Also you need to populate data into the custom setting abc_EndPoint__c
        This is where you are arranging the test data
        */
        profile p =[select id from Profile WHERE Name ='Standard User' LIMIT 1];       
         User user = new User();
        //Populate data for rest of the fields
        user.Alias = 'rrn';
        user.username = 'ganga@g.com';
        user.Email = 'rg@h.com';
        user.CommunityNickname ='raj';
        user.ProfileId = p.id;
        user.LastName = 'ganga';
        user.TimeZoneSidKey = 'America/Los_Angeles';
        user.LocaleSidKey = 'en_US';
        user.EmailEncodingKey = 'UTF-8';
        user.LanguageLocaleKey = 'en_US';
        user.Okta_Id__c = 'hi';
       
        insert user;
      
        EF_Request__c efreqobj = new EF_Request__c();
    
     efreqobj.Okta_Id__c = 'abc';
     insert efreqobj;
    
    EF_Requested__c efreqstedobj = new EF_Requested__c();
   
    efreqstedobj.EF_Request_ID__c = efreqobj.id ;
   
    efreqstedobj.Request_Type__c = 'Phone';
   
   insert  efreqstedobj;
  
   EF_Resource_Metadata__c efresourceobj =  new EF_Resource_Metadata__c();
  
   efresourceobj.Name = 'abhi';
   efresourceobj.OKTA_App_ID__c ='abcd';
  
   insert efresourceobj ;
  
  
   EF_OKTA_Queue__c efoktaQ = new EF_OKTA_Queue__c ();
 
    efoktaQ.EF_Requested_Resource__c = efreqstedobj.id;
    efoktaQ.OKTA_JSON__c = 'Hi';
    efoktaQ.OKTA_Response__c = 'hi this is a test';
    efoktaQ.CurrencyIsoCode = 'USD';
    efoktaQ.status__c = 'Request Sent';
    efoktaQ.Number_Tried__c = 8;
   
    insert efoktaQ;
   
   
     OKTA_EndPoint__c customSetting = new OKTA_EndPoint__c();
        //Populate data for the data set 'abc'
        customSetting.Name = 'testingendpoint';
        insert customSetting;
       
        Test.setMock(HttpCalloutMock.class, new  EF_UpdateOKTA_MockHttpResponseGenerator());
      
        Test.startTest();
        EF_UpdateOKTA testObj = new EF_UpdateOKTA();
       
        Test.stopTest();
      
  
        EF_OKTA_Queue__c q = [Select Status__c from EF_OKTA_Queue__c where Id = :efoktaQ.id];
        System.assert(q.Status__c == 'Complete');
      
    }
}

with one mocktest callout class written in another class already
now the Error message is 

System.NullPointerException: Attempt to de-reference a null object


Class.EF_UpdateOKTA.UpdateEFKotaQueue: line 39, column 1
Class.EF_UpdateOKTA.<init>: line 5, column 1
Class.EF_UpdateOKTA_Test.testCallout: line 78, column 1

Thanks in Advance