Hi,

I am able to cover Trigger.IsInsert & Trigger.IsUpdate but Trigger.IsDelete is not covering. Please check below test class and provide your suggestions.

Trigger:-
trigger CMC_Post_Tention_Weight_Rollup on OpportunityLineItem (after Insert, After Delete, After Update) 
{
Product2 productPostTensionWeight = [select id, name From Product2 where name = 'Post tension'];
    
if(trigger.isInsert)
{
List <OpportunityLineItem> postTensionWeight = trigger.new; //for update/Insert    
List<Id> listOptyIds = new List<Id>(); 
for(OpportunityLineItem eachOptyLineItem : PostTensionWeight ) 
    {
    listOptyIds.add(eachOptyLineItem.OpportunityId); 
    }

List <Opportunity> AllOppty = [Select ID, Name, Total_Post_Tension_Weight__c  from Opportunity 
                               where id in: listOptyIds];
for(Opportunity opty:AllOppty)
    {
    for(OpportunityLineItem PTW : postTensionWeight)
        {
          
        if(PTW.Product2Id == productPostTensionWeight.Id && PTW.OpportunityId == opty.Id)
            {   
            Opty.Total_Post_Tension_Weight__c = Opty.Total_Post_Tension_Weight__c + PTW.Post_Tension_Weight__c;   
            
            }
         }    
     }
update AllOppty;
}

if(trigger.isDelete)
{
List <OpportunityLineItem> postTensionWeight = trigger.Old; //for Delete    
List<Id> listOptyIds = new List<Id>(); 
for(OpportunityLineItem eachOptyLineItem : PostTensionWeight ) 
    {
    listOptyIds.add(eachOptyLineItem.OpportunityId); 
    }

List <Opportunity> AllOppty = [Select ID, Name, Total_Post_Tension_Weight__c  from Opportunity 
                               where id in: listOptyIds];
for(Opportunity opty:AllOppty)
    {
    for(OpportunityLineItem PTW : postTensionWeight)
        {
      
        if(PTW.Product2Id == productPostTensionWeight.Id && PTW.OpportunityId == opty.Id)
            {
           Opty.Total_Post_Tension_Weight__c = Opty.Total_Post_Tension_Weight__c - PTW.Post_Tension_Weight__c;   
            
            }
         }    
     }

update AllOppty;
}

if(trigger.isUpdate)
{
List <OpportunityLineItem> postTensionWeight = trigger.New;
List <OpportunityLineItem> OldpostTensionWeight = trigger.Old;    
List<Id> listOptyIds = new List<Id>(); 
for(OpportunityLineItem eachOptyLineItem : PostTensionWeight ) 
    {
    listOptyIds.add(eachOptyLineItem.OpportunityId); 
    }

List <Opportunity> AllOppty = [Select ID, Name, Total_Post_Tension_Weight__c  from Opportunity 
                               where id in: listOptyIds];
for(Opportunity opty:AllOppty)
    {
    for(OpportunityLineItem PTW : postTensionWeight)
        {
        For(OpportunityLineItem OPTW : OldpostTensionWeight)
        {        
        if(PTW.Product2Id == productPostTensionWeight.Id && PTW.OpportunityId == opty.Id && PTW.ID==OPTW.ID)
            {
      
            Opty.Total_Post_Tension_Weight__c = Opty.Total_Post_Tension_Weight__c - OPTW.Post_Tension_Weight__c + PTW.Post_Tension_Weight__c;   
            
            }
         }
        }     
     }

update AllOppty;
}
   
} 

Test Class:- 

@istest(SeeAllData = true)
public with sharing class testupdateoppty{
 public static testMethod void TestdeletetonneageMethod() 
    {
      Opportunity op3 = new Opportunity(Name='Testoppthhhhhhssssde');
         
      op3.Bid_Date_Time__c = system.today();
      op3.CloseDate = system.today();
      op3.Market_Segment__c = 'Test1';
      op3.Stage_Structural__c = 'Planning';
      op3.State__c = 'AK';
      op3.City__c = 'Test';
      op3.Opportunity_Type__c = 'Test2';             
      op3.Referred_To__c = 'Test3';
      op3.Referred_From__c = 'Test4';
      op3.Sales_Office__c = 'Test6';
      op3.StageName = 'Planning';
      op3.Total_Loose_Dowel_Revenue__c = 1234;
      op3.Total_TBA_Revenue__c = 200000;
      op3.Total_Loose_Dowel_Revenue__c=1000;
      op3.Total_Loose_Dowel_Tons__c= 2000;
      op3.Dummy_Tonnage__c = 23 ;
      insert op3;
      
       Pricebook2 pb1 = [select Id from Pricebook2 where isStandard=true limit 1];                          
       Product2 prod1 = new Product2(Name = 'Loose Dowels123', ProductCode = 'LB');        
       insert prod1;
       
     
       
        PricebookEntry price = new PricebookEntry(
            
            Pricebook2Id = pb1.Id,
            UnitPrice = 1.0,
            IsActive = true,
            Product2Id = prod1.Id
            
            );
            insert price;
       
      
                 
      List<opportunityLineItem> opppro1 = new opportunitylineitem[]{new opportunitylineitem(UnitPrice=10000.00,
      Quantity=10,Total_Revenue__c = 10000.00, opportunityid=op3.id, pricebookEntryId=Price.id, Invoiced__c = TRUE)};
           
            insert opppro1;   
    
    op3.Dummy_Tonnage__c  = 50;
           update op3;
            
          Test.startTest();
           delete op3;
          Test.stopTest();
    }
}