trigger populateProductFamily  on OpportunityLineItem (after Insert,before delete) {
  
  
  if((trigger.IsAfter  && trigger.IsInsert)  || (trigger.IsBefore  && trigger.IsDelete)  )      // run after insert and before delete
  
  
  {
    //map to hold product family for a gven oppty
    Map<id,Set<String>> oppprodFamilyMap = new Map<id,Set<String>>();
    //get all oppty id
    List<id> oppId =  new List<Id>();
    List<opportunitylineitem> triggerList = new List<opportunitylineitem>();
    if(trigger.IsDelete)
    {  system.debug('in delete');
    triggerList = trigger.old;
  }
  
  else
  {
    triggerList = trigger.new;
  }
  
  
  for (opportunitylineitem ol : triggerList )  {
    
    oppId.add(ol.opportunityid);
    
  }
  
  // query all opportunity for opportunitylineitem inserted
  
  
  
  List<opportunity> oppList = [select id ,Opportunity_Product_Family__c from opportunity where id in :oppId];
  
  
  
  
  // query all opportunitylineitem linked with opportunity of current opportunitylineitem
  //we need this so that we can get all product family for a a given oppty
  
  List<opportunitylineitem> olList  =  new List<opportunitylineitem>();
  
  if(trigger.IsDelete) {
    olList = [select id,opportunityid,product2.family  from opportunitylineitem where opportunityid in :oppList  and id not in  :triggerList  ];
    
  }
  
  else
  
  {
    olList = [select id,opportunityid,product2.family  from opportunitylineitem where opportunityid in :oppList  ];
    
  }
  
  system.debug('---ollist' + olList  );
  
  
  //now we need to separate productfamily by opportunity
  
  
  for (opportunitylineitem ol : olList )  {
    
    IF(ol.product2.family  != null)  {
      if(oppprodFamilyMap.get(ol.opportunityid) != null)  {
        
        Set<String>  pFamilySet   = oppprodFamilyMap.get(ol.opportunityid);
        pFamilySet.add(ol.product2.family);
        oppprodFamilyMap.put(ol.opportunityid,pFamilySet);
        
      }
      
      else {
        Set<String> pFamilySet = new Set<String> ();
        pFamilySet.add(ol.product2.family);
        oppprodFamilyMap.put(ol.opportunityid,pFamilySet);
        
        
      }
      
    }
    
    
    
  }
  
  
  
  // now we have got all productfamily for a given oppty.
  //we need to concat  and update field
  
  
  //opplist to update
  
  List<opportunity> oppListToUpdate = new List<opportunity>();
  
  
  for(opportunity  o : oppList)
  {
    
    
    List<String>  pFamilyList = new List<String>(oppprodFamilyMap.get(o.Id));
    String pFamily  = string.join(pFamilyList ,',');
    
    o.Opportunity_Product_Family__c  = pFamily;
    oppListToUpdate.add(o);
    
    
    
    
  }
  
  
  if(oppListToUpdate.size()>0)
  
  update  oppListToUpdate;
  
  
  
  
  
  
  
}

}

@isTest public class populateProductFamilyTest{

    //method 1 - create OLI's
    private static testMethod void createOlis(){
          // create account
          Account act = new Account();
          act.Name = 'test account';
          INSERT act;

          //create Opportunity
          Opportunity opp 	= new Opportunity();
          opp.Name 			= 'test Opp';
          opp.AccountId 	= act.Id;
          opp.Type 			= 'System';
          opp.RecordTypeId  = [SELECT id 
                                 FROM RecordType 
                                WHERE SObjectType='Opportunity' 
                                  AND DeveloperName=:opp.type].id; 
          opp.StageName     = 'Prospecting';
          opp.CloseDate     = Date.today();
          INSERT opp;

          // create product
          Product2 prod1 	= new Product2();
          prod1.Name        = 'test product 1';
          prod1.Family      = 'Systems';
          prod1.IsActive 	= true;        
          INSERT prod1;

        // create price book entry for this product
        PriceBookEntry pbe1 = new PriceBookEntry(PriceBook2Id = Test.getStandardPricebookId(), 
                                                   Product2Id = prod1.Id,   
                                                   UnitPrice=100, 
                                                   IsActive=true);
        INSERT pbe1;                                           
         
        // create product
        Product2 prod2  = new Product2();
        prod2.Name      = 'test product 2';
        prod2.Family    = 'Device';
        prod2.IsActive 	= true;        
        INSERT prod2;

       // create price book entry for this product
       PriceBookEntry pbe2 = new PriceBookEntry(PriceBook2Id = Test.getStandardPricebookId(), 
                                                  Product2Id = prod2.Id,   
                                                  UnitPrice=100, 
                                                  IsActive=true);

        INSERT pbe2;

        // Create 1st OLI with licensed product --> this will trigger after insert trigger
		OpportunityLineItem oli1 = new OpportunityLineItem();
		oli1.OpportunityId       = opp.Id;
        oli1.Quantity            = 2;        
        oli1.PriceBookEntryId    = pbe1.Id;
        oli1.UnitPrice           = pbe1.UnitPrice;    
		INSERT oli1; 

        // Create 2nd OLI with licensed product --> this will trigger after insert trigger
		OpportunityLineItem oli2 = new OpportunityLineItem();
		oli2.OpportunityId       = opp.Id;
        oli2.Quantity            = 2;        
        oli2.PriceBookEntryId    = pbe2.Id;
        oli2.UnitPrice           = pbe2.UnitPrice;    
		INSERT oli2; 

    }

    // method 2 - delete OLI's
        private static testMethod void deleteOlis(){

        // create account
        Account act = new Account();
        act.Name    = 'test account';
        INSERT act;

        //create Opportunity
        Opportunity opp  = new Opportunity();
        opp.Name 		 = 'test Opp';
        opp.AccountId    = act.Id;
        opp.Type 		 = 'System';
        opp.RecordTypeId = [SELECT id 
                              FROM RecordType 
                             WHERE SObjectType='Opportunity' 
                               AND DeveloperName=:opp.type].id; 
       opp.StageName     = 'Prospecting';
       opp.CloseDate     = Date.today();
       INSERT opp;

       // create product
       Product2 prod1 	 = new Product2();
       prod1.Name        = 'test product 1';
       prod1.Family      = 'Systems';
       prod1.IsActive 	 = true;        
       INSERT prod1;

      // create price book entry for this product
      PriceBookEntry pbe1 = new PriceBookEntry(PriceBook2Id = Test.getStandardPricebookId(), 
                                                 Product2Id = prod1.Id,   
                                                 UnitPrice=100, 
                                                 IsActive=true);
      INSERT pbe1;                                           
       
      // create product
      Product2 prod2  = new Product2();
      prod2.Name      = 'test product 2';
      prod2.Family    = 'Device';
      prod2.IsActive  = true;        
      INSERT prod2;

     // create price book entry for this product
     PriceBookEntry pbe2 = new PriceBookEntry(PriceBook2Id = Test.getStandardPricebookId(), 
                                                Product2Id = prod2.Id,   
                                                UnitPrice=100, 
                                                IsActive=true);
      INSERT pbe2;                                          

      // Create 1st OLI with licensed product --> this will trigger after insert trigger
      OpportunityLineItem oli1 = new OpportunityLineItem();
      oli1.OpportunityId       = opp.Id;
      oli1.Quantity            = 2;        
      oli1.PriceBookEntryId    = pbe1.Id;
      oli1.UnitPrice           = pbe1.UnitPrice;    
      INSERT oli1; 

      // Create 2nd OLI with licensed product --> this will trigger after insert trigger
      OpportunityLineItem oli2 = new OpportunityLineItem();
      oli2.OpportunityId       = opp.Id;
      oli2.Quantity            = 2;        
      oli2.PriceBookEntryId    = pbe2.Id;
      oli2.UnitPrice           = pbe2.UnitPrice;    
      INSERT oli2; 

      // now we need to run before delete trigger, thus delete the Olis now
      DELETE oli1;
      DELETE oli2;    
    }

}