@Mukesh_SfdcDev , {!Piyush_soni__c} : I am not getting any excpetion or error my test class runs susccessfully . But I am having problem with code coverage . My test class is not covering 75% coverage as my Trigger UpdateMostRecentOpportunityStageOfContact  is showing only 42% coverage but I need atleast 75% so that I can deploy it on production. Here is my updated test class which covering 42% coverage Ignore prevoius one. Please let me know what I need to add in test class to make 75 % coverage .

I have also attached a screen shot of my trigger coverage where red lines are not being coevered.

Test Class :
@isTest
public class TestUpdateMostRecentopportunityStage {
   static testMethod void TestUpdateStageOnContactTest()
  {   
    Account a = new Account(Name = 'TestUpdateStageOnContactTest');
    a.Type = 'Prospect';
    insert a;

    Contact newContact = new Contact(Lastname='TestUpdateStageOnContactTest', AccountId = a.Id ,Email='mayank06@gmail.com' );
    insert newContact;
  
        String opportunityName = 'TestUpdateStageOnContactTest';
      
        Opportunity o2 = new Opportunity(AccountId=a.Id, name='OPP test1', StageName='Demo', CloseDate = Date.today() );
       insert o2;
        OpportunityContactRole ocr1 = new OpportunityContactRole(OpportunityId = o2.Id, ContactId = newContact.Id, Role='Decision Maker',Isprimary=true );
    insert ocr1;
    
          Test.StartTest();
        o2.stageName='Demo';
        update o2;
        newContact.Most_recent_Opportunity_Stage__c='Demo';
        update newContact;
        
        Test.StopTest();
         
      }   
}