trigger UpdateSelfLookUpField on npe4__Relationship__c(before insert,before update,after update) {
     npe4__Relationship__c acc,acc1;
     List<npe4__Relationship__c >acc2=new List<npe4__Relationship__c >();
     
     Set<id> act=new set<id>();
     
        if(trigger.isbefore){
            for(npe4__Relationship__c ac: Trigger.new){ 
            acc1=ac;          
                if( ac.npe4__SYSTEM_SystemCreated__c){
                    ac.city__c=ac.CityUpdate__c;
                    ac.Cohort__c=ac.CohertUpdate__c;
                    ac.Programme__c=ac.ProgrammeUpdate__c;
                    ac.Placement_Engagement__c=ac.Placement_engagemen_update__c;
                    ac.Mentor_engagement__c=ac.Mentor_engagement_Update__c;
                    ac.recordtypeid=ac.Record_Type_parent__c; 
                    ac.Organisation__c=ac.Placement_organisation_Update__c;
                    ac.Placement_Opportunity__c=ac.Placement_Opportunity_Update__c;
                   system.debug('@@@@@@@@22222222222'+ac);
              }
           }
       }
       if(trigger.isafter){
           for(npe4__Relationship__c ac1:Trigger.new){
          system.debug('@@@@@@@@>>>>>>>>'+ac1.npe4__SYSTEM_SystemCreated__c);
               if(!ac1.npe4__SYSTEM_SystemCreated__c)
               system.debug('@@@@@@@@11111111'+ac1.npe4__ReciprocalRelationship__c);
                   act.add(ac1.npe4__ReciprocalRelationship__c);
           }  system.debug('@@@@@@@@33333333'+act.size());
              system.debug('@@@@@@@@33333333'+act);
           if(act.size()>0){
               npe4__Relationship__c rl=[Select id,Organisation__c,npe4__Type__c,Type_Update__c from npe4__Relationship__c where id In :act limit 1];
              
               if(rl!=null){
               
                   update rl;
               }
           } 
       }    
       
}


>>>>>>>>>>>>>>>>>>>>>Test class

@isTest

public class UpdateSelfLookUpFieldTest {

    static testmethod void UpdateSelfLookUpFieldTest (){
    
    Account acc=new Account();
    acc.name='test';  
    insert acc;    
     
    Contact con=new Contact();
    con.lastname='test';
    con.firstname='test';
    con.accountid=acc.id;   
    insert con; 
    
    npe4__Relationship__c acr=new npe4__Relationship__c();
    acr.npe4__Contact__c=con.id;
    acr.npe4__Status__c='Current';
    acr.city__c='Paris';
    acr.Cohort__c='2011';
    acr.Programme__c='abc';
    acr.Placement_Engagement__c='123';
    acr.Mentor_engagement__c='1';
    acr.npe4__SYSTEM_SystemCreated__c= false;    
    insert acr;
    
    
    npe4__Relationship__c ac=new npe4__Relationship__c();
    ac.npe4__Contact__c=con.id;
    ac.npe4__Status__c='Current';
    ac.city__c='Paris';
    ac.Cohort__c='2011';
    ac.Programme__c='abc';
    ac.Placement_Engagement__c='123';
    ac.Mentor_engagement__c='1';
    ac.npe4__SYSTEM_SystemCreated__c= false;  
    ac.npe4__ReciprocalRelationship__c= acr.id;   
    insert ac;
    
    npe4__Relationship__c ac2=new npe4__Relationship__c();
    ac2.npe4__Contact__c=con.id;
    ac2.npe4__Status__c='Current';
    ac2.city__c='Paris';
    ac2.Cohort__c='2011';
    ac2.Programme__c='abc';
    ac2.Placement_Engagement__c='123';
    ac2.Mentor_engagement__c='1';
    ac2.npe4__SYSTEM_SystemCreated__c= true; 
    ac2.npe4__ReciprocalRelationship__c= ac.id;   
    insert ac2;
    
    
    npe4__Relationship__c ac3=[Select id,npe4__Status__c,npe4__ReciprocalRelationship__c,npe4__ReciprocalRelationship__r.city__c from npe4__Relationship__c where id=:ac2.id ];
   
   // ac3.npe4__SYSTEM_SystemCreated__c=false;
   //  ac3.npe4__ReciprocalRelationship__c=acr.id;
    //update ac3;
    
    
    
      }

}




>>>>>>>>>>>>>>>value not coming in debug.... system.debug('@@@@@@@@11111111'+ac1.npe4__ReciprocalRelationship__c);