I am new to test classes, but Im pulling my hair on this one. 

Below is my trigger to create an invoice from Quote once opp is closed and quotetoinvoice checkbox is ticked: 

trigger CreateInvoice on Opportunity (after update, after insert) {
    List<Invoice__c> invoiceList = new List<Invoice__c>();
    List<InvoiceLineItem__c> invoiceLineItemList = new List<InvoiceLineItem__c>();
    Set<Id> oppIdSet = new Set<Id>();
    
    // We only care about opportunities that are closed won
    for(Opportunity o : trigger.new)
    {
        if (o.stagename=='Closed Won')
        {
            oppIdSet.add(o.id);
        }
    }

    // Need to grab all the quotes and their subsequent quotelineitems under all the opportunities that fired the trigger, but select quotes that has QuotetoInvoice=True
    List<Quote> quoteList = [SELECT id, quotenumber, Accountid, BillingStreet, BillingCity, BillingState, BillingPostalCode, BillingName, Shippingname, ShippingStreet, ShippingCity, ShippingPostalCode, ShippingState, REP__c, Totalprice, Opportunityid, name, QuotetoInvoice__c, 
                (SELECT id, ListPrice, PricebookEntry.name, PricebookEntry.ProductCode, TotalPrice, Quantity FROM quotelineitems) 
                FROM Quote WHERE Opportunityid in: oppIdSet AND QuotetoInvoice__c=TRUE]; 
    
    // Create an invoice for each quote
    for (Quote q : quoteList)
    {
        Invoice__c newInvoice = new Invoice__c();
        newInvoice.Invoice_number__c=q.quotenumber;
        newInvoice.opportunity__c= q.Opportunityid;
        newInvoice.Bill_To__c=q.Billingname;
        newInvoice.BillingStreet__c=q.Billingstreet;
        newInvoice.BillingCity__c= q.BillingCity;
        newInvoice.BillingState__c= q.BillingState;
        newInvoice.BillingZip__c= q.BillingPostalCode;
        newInvoice.Ship_To__c=q.Shippingname;
        newInvoice.ShippingStreet__c=q.Shippingstreet;
        newInvoice.ShippingCity__c= q.ShippingCity;
        newInvoice.ShippingState__c= q.ShippingState;
        newInvoice.ShippingZip__c= q.ShippingPostalCode;
        newInvoice.Total__c=q.Totalprice;
        newInvoice.Customer__c=q.Accountid;
        newInvoice.REP__c=q.REP__c;
        invoiceList.add(newInvoice);
    }
    
    // We need to insert the invoices first, before being able to insert the invoicelineitems under it.
    insert invoiceList;
    // Construct this set as a copy of the invoiceList so we can remove from it easily later
    Set<Invoice__c> invoiceSet = new Set<Invoice__c>(invoiceList);
    
    // Create the invoicelineitems
    for (Quote q : quoteList)
    {
        for (QuoteLineItem qli : q.quotelineitems)
        {
            InvoiceLineItem__c newInvLineItem = new InvoiceLineItem__c();
            newInvLineItem.Invoiceid__c=qli.id;
            newInvLineItem.Amount__c = qli.ListPrice;
            newInvLineItem.Item__c = qli.PricebookEntry.ProductCode;
            newInvLineItem.Description__c= qli.PricebookEntry.name;
            newInvLineItem.Quantity__c= qli.quantity;
            
            // We need to relate the invoicelineitem to the correct invoice
            for (Invoice__c i : invoiceSet)
            {
                // Using quote number as an identifier
                if (i.Invoice_Number__c == q.quotenumber)
                {
                    newInvLineItem.Invoiceid__c= i.id;
                }
            }
            invoiceLineItemList.add(newInvLineItem);
        }
        
        // We need to remove the invoice we just used from the set, just in case there are quotes with duplicate quote numbers.
        for (Invoice__c i : invoiceSet)
        {
            if (i.name == q.name)
            {
                invoiceSet.remove(i);
            }
        }
    }
    
    insert invoiceLineItemList;

And this is my test class: 

@isTest
private class CreateInvoiceTestClass {
    @isTest static void insertOpp() {
        Account acc = new Account (name='Acme');
        insert acc;
        Opportunity opp= new Opportunity ();
        opp.name= 'Testopp';
        Opp.Accountid= acc.id;
        opp.CloseDate= date.today();
        opp.StageName= 'Qualification';
        insert opp;

Pricebook2 pb = new Pricebook2(Name = 'Standard Price Book 2009', Description = 'Price Book 2009 Products', IsActive = true );
    insert pb;
Product2 prod = new Product2(Name = 'SLA: Bronze', IsActive = true);
    insert prod;

Pricebook2 standardPB = [select id from Pricebook2 where isStandard=true];
PricebookEntry standardPBE = new PricebookEntry(Pricebook2Id = standardPB.Id, Product2Id = prod.Id, UnitPrice = 1000, IsActive = true);
    insert standardPBE;
PricebookEntry pbe = new PricebookEntry(Pricebook2Id = pb.Id, Product2Id = prod.Id, UnitPrice = 1000, IsActive = true);
    insert pbe;
        
       
        Quote q= new Quote ();
        	 q.Name= 'Testq';
        	q.OpportunityId= Opp.id;
         	q.quotetoinvoice__C= TRUE;
         	q.REP__C= 'AC' ;
        	q.BillingStreet= '123';
        	q.BillingCity= 'City';
        	q.BillingPostalCode= '12345';
        	q.Pricebook2Id= pb.id;
        	insert q;
       
      QuoteLineItem qli= new QuoteLineItem(id=q.Id, Product2id='Product', PricebookEntryid= pbe.Id,  quantity=2);
        insert qli;
        opp.StageName= 'Closed Won';

									}
    
}

Keep getting error:  System.QueryException: List has no rows for assignment to SObject,   Class.CreateInvoiceTestClass.insertOpp  line 18

Please help.