I'm not write test class is full loop. Because ploblem adderror method.

trigger RelationDuplicationA2A on Relationship__c(before insert) {
set<ID> setAccountID = new set<ID>();
set<ID> setRevAccountID = new set<ID>();
integer setRecordType;

for(Relationship__c ra: Trigger.new){
   if(ra.Account_ID__r.Mark_for_Delete__c != true || ra.Rev_Account_ID__r.Mark_for_Delete__c  != true && (ra.RecordTypeID == '01290000000Ym1W')){
       if (Trigger.new[0].Account_ID__c != NULL && Trigger.new[0].Rev_Account_ID__c != NULL)  {
           setAccountID.Add(ra.Account_ID__c);  //Set Value Relation Account to Account
           setRevAccountID.Add(ra.Rev_Account_ID__c);
           setRecordType = 1;  //set value criteria
       }  
   }
    
}
//------------------------------------------- End Add Data --------------------------------------------------------------------------------------------------

// SOQL for Duplicate Relationship without Loop
    if(setRecordType == 1){
           List<Relationship__c> rs = [ select id,Account_ID__c,Rev_Account_ID__c,Mark_for_Delete__c from Relationship__c  WHERE Account_ID__c = :Trigger.new[0].Account_ID__c And Rev_Account_ID__c =: trigger.new[0].Rev_Account_ID__c And Mark_for_Delete__c =: false];
               
               if (rs.size() > 0 ) {
                   Trigger.new[0].Account_ID__c.addError('Duplicate Relationship');
                   Trigger.new[0].Rev_Account_ID__c.addError('Duplicate Relationship');
               }
     }
}

 Ploblem Trigger Line : 

Trigger.new[0].Account_ID__c.addError('Duplicate Relationship');                 Trigger.new[0].Rev_Account_ID__c.addError('Duplicate Relationship');

@isTest
private class TestRelationDuplicationA2A  {
   static testMethod void myUnitTest() {
      Account Acc = new Account(Name = 'test',AccountNumber = '00000001');
         insert Acc;
      Contact Con = new Contact(LastName = 'test',AccountID = Acc.id);
         insert con;
      
      Relationship__c ra = new Relationship__c(Account_ID__c = Acc.id,Rev_Account_ID__c = Acc.id,Mark_for_Delete__c = False);
         try{      
            insert ra;
            }catch(DMLException de){

        }  
      Relationship__c Dup = new Relationship__c(Account_ID__c = Acc.id,Rev_Account_ID__c = Acc.id,Mark_for_Delete__c = False);
             try {
             insert Dup;
             }
             catch (Exception e) {
                   System.debug('Duplicate Relationship');                        
             } 
  }
}

 Thank you so much.