Hi Swati, thanks for your response.
 
Here's the function which is called by an after insert trigger on the Opportunity:

/* This function inserts an initial contact role on an opportunity for the contact from which it was created*/
    public static void InitializeContactRoles(Opportunity[] newOpps){

        /* when an opportunity is created, there should be a built-in opportunity contact role created also.  
           query that and use it to fill in a new Contact_Role__c*/
        List<Id> OppIds = new List<Id>();
        for (Opportunity opp: newOpps){
            OppIds.add(opp.Id);
        }
        
        List<OpportunityContactRole> ocrList = [Select Id, ContactId, OpportunityId from OpportunityContactRole where OpportunityId in :OppIds];
        
        List<Contact_Role__c> newRoles = new List<Contact_Role__c>();
        for (OpportunityContactRole ocr : ocrList){
            newRoles.add(new Contact_Role__c(Contact__c=ocr.ContactId, Opportunity__c=ocr.OpportunityId, Roles__c='Sponsor (Coach)'));
        }
        
        insert newRoles;
               
    }

@isTest
public class Opportunity_TriggerTest {

    public static TestMethod void runTest(){
        Account testAccount = new Account(Name='AxonifyTest89u7245987432897234879324');
        insert testAccount;
        
        Contact testContact = new Contact(LastName='TestContact293847', AccountID=testAccount.Id);
        insert testContact;

        Opportunity testOpp = new Opportunity(Name='TestOpportunity78453757755743566', 
                                              AccountID=testAccount.Id,
                                              StageName = 'Stage F - (ODR/Sales Prospecting)',
                                              CloseDate = Date.today()
                                             );
        insert testOpp;
        
        //Here is where the Trigger Fires
        //It looks up any OpportunityContactRole record on the newly-inserted Opportunity.
        //But because of the context, the OpportunityContactRole is not there yet.
        //The test below therefore fails

        List<Contact_Role__c> results = [Select Id from Contact_Role__c where Opportunity__c = :testOpp.Id];
        
        System.assert(results.size()>0);  // fails because results is empty
    }
}