Hi, I have a trigger in place that updates the product schedule dates if the Opportunity close date changes.  The trigger works exactly as expected, however, I'm unable to test it adequately. The test logic does not insert the default product schedules automatically, so I'm trying to insert them manually so I can generate adequate coverage. However, the code fails on insert when I try to insert the OpportunityProductSchedule record, the error is: 

System.DmlException: Insert failed. First exception on row 0; first error: INSUFFICIENT_ACCESS_ON_CROSS_REFERENCE_ENTITY, insufficient access rights on cross-reference id: []

When I looked up the Object reference for OpportunityLineItemSchedule, it shows as createable so I'm not sure what the issue is - anyone been able to test product schedules? All of the posts I found it looks like other people are having the same issues and am not finding any resolutions posted. 

APEX Trigger and Class: 
trigger updateProdScheduleTrigger on Opportunity (after update) {
   
    Set<id> olisIds = new Set<id>();
    Set<id> opptyIds = new Set<id>();
   
    for(Opportunity o : trigger.new){
        if(o.CloseDate != trigger.oldMap.get(o.id).CloseDate){
     opptyIds.add(o.id);
        }
    }
    if(!opptyIds.isEmpty()){
    List<OpportunityLineItem> oli = [SELECT id FROM OpportunityLineItem WHERE OpportunityId IN :opptyIds AND HasRevenueSchedule = TRUE];
        if(!oli.isEmpty()){
            for(OpportunityLineItem olis : oli){
                olisIds.add(olis.id);
            }
        }
        updateProductSchedule.updateSchedule(olisIds);
    }

}

public class updateProductSchedule{
   
   
    public static void updateSchedule(Set<id> olisIds){
       
        List<OpportunityLineItem> olis = [SELECT id, OpportunityId, Opportunity.CloseDate, UnitPrice
                                          FROM OpportunityLineItem
                                          WHERE Id IN :olisIds];
        Map<String, Date> lineCloseDate = new Map<String, Date>();
        for(OpportunityLineItem o : olis){
            lineCloseDate.put(o.id, o.Opportunity.CloseDate);
        }
       
        List<OpportunityLineItemSchedule> oliSchedules = new List<OpportunityLineItemSchedule>();
       
  oliSchedules = [SELECT id, ScheduleDate, OpportunityLineItemId, Quantity, Revenue, Type, OpportunityLineItem.UnitPrice,
                        OpportunityLineItem.OpportunityId, OpportunityLineItem.Opportunity.CloseDate
                        FROM OpportunityLineItemSchedule
                        WHERE OpportunityLineItemId IN :olisIds ORDER BY ScheduleDate ASC];
      
        for(OpportunityLineItemSchedule os : oliSchedules){
            system.debug('current os schedule date>>>'+os.ScheduleDate +  ' and revenue>>>'+os.Revenue);
        }
   List<OpportunityLineItemSchedule> olischedToUpdate = new List<OpportunityLineItemSchedule>();       
       
       
        Date newStartSchedDate = oliSchedules[0].OpportunityLineItem.Opportunity.CloseDate;
        Decimal newREvScheduleAmt = oliSchedules[0].OpportunityLineItem.UnitPrice / 12;
        for(Integer i = 0; i<oliSchedules.size(); i++){
            oliSchedules[i].Revenue = newRevScheduleAmt;
            oliSchedules[i].ScheduleDate = newStartSchedDate.addMonths(i);
            olischedToUpdate.add(oliSchedules[i]);
            system.debug('current os schedule date>>>'+oliSchedules[i].ScheduleDate +  ' and revenue>>>'+oliSchedules[i].Revenue);
        }
        update olischedToUpdate;
      
    }

}

TEST Code: 

@istest (seeAlldata=True)
public class testUpdateProdSchedule{
    private testmethod static void testUpdateSched(){
       
        List<Account> accts = new List<Account>();
        for(integer i=0; i<200; i++){           
            Account a = new Account(Name='test'+i);
            accts.add(a);
        }
        insert accts;
       
        List<Opportunity> opptys = new List<Opportunity>();
        for(integer i=0; i<200; i++){
            Opportunity o = new Opportunity(Name='test'+i, AccountId = accts[i].id, CloseDate=date.today().addMonths(12),
                                            Amount=0, StageName='Proposed');
            opptys.add(o);
        }
        insert Opptys;
        Set<id> opptyIds = new Set<Id>();
        for(Opportunity o : opptys){
            opptyIds.add(o.id);
        }
        PricebookEntry pbe = [SELECT id, UnitPrice, Product2.NumberOfRevenueInstallments FROM PriceBookEntry
                              WHERE isActive=True
                              AND Product2.NumberOfRevenueInstallments = 12 LIMIT 1];
       
        system.debug('number of rev installments for pbe>>>'+pbe.Product2.NumberOfRevenueInstallments);
       
        List<OpportunityLineItem> olis = new List<OpportunityLineItem>();
        for(integer i=0; i<200; i++){
         OpportunityLineItem oli = new OpportunityLineItem();
            oli.OpportunityId=opptys[i].id;
            oli.PricebookEntryId=pbe.id;
            oli.Quantity=1;
            oli.UnitPrice=1200000;
            olis.add(oli);
        }
        insert olis;
        OpportunityLineItem line = [SELECT id FROM OpportunityLineItem WHERE PriceBookEntryId=:pbe.id LIMIT 1];
        List<OpportunityLineItemSchedule> oliSchedToInsert = new List<OpportunityLineItemSchedule>();
        for(integer i=0; i<12; i++){
            OpportunityLineItemSchedule s = new OpportunityLineItemSchedule();
            s.Revenue = 100000;
            s.ScheduleDate = date.today().addMonths(i);
            s.OpportunityLineItemId = line.id;
            s.type = 'Both';
            s.Quantity = 1;
           
            oliSchedToInsert.add(s);
        }
        insert oliSchedToInsert;
       
        List<OpportunityLineItemSchedule> oliSched = [SELECT id, Revenue, ScheduleDate,OpportunityLineItemId,
                                                      OpportunityLineItem.OpportunityId FROM OpportunityLineItemSchedule
                                                      WHERE OpportunityLineItem.OpportunityId IN : opptyIds];
       
        system.debug('size of schedule list>>>'+oliSched.size());
        //system.assertEquals(oliSched.size()>0, true);
        opptys[0].closeDate = date.today().addMonths(13);
        update opptys[0];
       
        List<Opportunity> opptysToUpdate = new List<Opportunity>();
       /* for(integer i=0;i<200; i++){
            opptys[i].CloseDate = date.today().addMonths(14);
            opptysToUpdate.add(opptys[i]);
        }
        update opptysToUpdate;*/
       
    }
}