“I am having problems with trigger test code coverage.  The following code is the original trigger:

trigger CreateImplementationCaseOnWin on Opportunity (before update) {

List<Case> CaseList = new List<Case> ();

for(Opportunity o: Trigger.new) {

String opptyId = o.AccountId;

Opportunity oldopp = trigger.OldMap.get (o.id);
       if (o.isWon != oldopp.isWon)

if(o.isWon == true && o.Type == 'New Business' && o.HasOpportunityLineItem == true && o.StageName == '990 - Closed/Won' ){


  Case c = new Case();
  c.AccountId = o.AccountId;
  c.OwnerId = o.OwnerId;
  c.Subject = o.Name;
  c.RecordTypeId = o.Case_Creation_RT__c;
  c.OB_Signed_Contract_Closed_Won__c = o.CloseDate;
  CaseList.add(c);


}

if(CaseList.size() > 0)
insert(CaseList);

} }

What I need to do is add another trigger with some tweaks to the if statement including removing o.iswon == true, changing type from 'New Business' to 'Existing Business' and changing the Stage from '90 - Closed/Won' to '08 - Contract Executed'.  So...

if(o.Type == 'Existing Business' && o.HasOpportunityLineItem == true && o.StageName == '08 - Contract Executed' )

However, when I do this and use the same test code from the original trigger above....the test code coverage drops dramatically. I try to make tweaks to that test code but it drops the coverage even further.  I am not sure what I am doing wrong.  Below is the original test code that covers 100% of the above code.  However, when I make the change to the if statement to the one in bold above, the coverage drops from 100% to 46%.  I tried adding the following code after insert oll in the original test code but it didn't seem to work.  I did have a question about if a custom field is set to required on the page layout when in StageName == '08 - Contract Executed, do i need to make sure those 'required' fields are in my test code?  I am very new to coding as you can probably tell!

oo.StageName= '08 - Contract Executed';
        oo.Type = 'Existing Business';

        update oo;
      
        Case c = new Case();
        c.AccountId = aa.Id;
        c.OwnerId = oo.OwnerId;
        c.Subject = oo.Name;
        c.RecordTypeId = oo.Case_Creation_RT__c;
        c.OB_Signed_Contract_Closed_Won__c = oo.CloseDate;
        insert c;

//original test code that covers 100% of the trigger at the top of this post

@isTest (SeeAllData=true)
private class Test_Class_CreateImplementationCaseOnWin {

    static testMethod void CreateImplementationCaseOnWin() {
 
        Account aa = new Account();
        aa.Name = 'Test Account';
        aa.Type = 'Customer';
        aa.BDM__c = 'Test User';
        aa.Time_Zone__c = 'Pacific';
        insert aa;
      
        Opportunity oo = new Opportunity();  
        oo.AccountId = aa.Id;
        oo.Name = 'test';
        oo.Amount = 1000;
        oo.StageName = 'Prospecting';
        oo.CloseDate = date.today();
        insert oo;
      
        //For production test class use 01u50000001F4l9
      
        OpportunityLineItem oll = new OpportunityLineItem();
        oll.OpportunityId = oo.Id;
        oll.Quantity = 1;
        oll.UnitPrice = 2.00;
        oll.PricebookEntryId = [SELECT Id FROM PricebookEntry WHERE isActive = true LIMIT 1].id;
      
        insert oll;
      
        oo.StageName= '90 - Closed/Won';
        update oo;
      
    //Verify that a case record was created
    for(Case cr : [SELECT Subject, Id FROM Case WHERE AccountId = :aa.Id LIMIT 1]){
    //System.assertEquals(cr.Subject = o.Name);
      
        }
      
        delete oll;
        delete oo;
      
      
      
    }
  
  
}”