Hello , 
can someone please help me ro resolve this error.
Challenge Not yet complete... here's what's wrong:
Ensure that you simulate a user visiting the product2New page by using the appropriate method in the System Test class.


Here is the code 
/**
 * @name TestDataFactory
 * @description Contains methods to construct and/or validate commonly used records
**/
public with sharing class TestDataFactory {

    /**
     * @name ConstructCollaborationGroup
     * @description
    **/
    public static CollaborationGroup ConstructCollaborationGroup(){
        //ToDo: Ensure this method returns a single Chatter CollaborationGroup
        //    whose Name starts with 'TEST' followed by the INVENTORY_ANNOUNCEMENTS constant
        //    and configured so anyone can join, see and post updates.
        CollaborationGroup grp = new CollaborationGroup();
        
        grp.Name='TEST'+Constants.INVENTORY_ANNOUNCEMENTS;
        grp.CollaborationType='Public';
        grp.IsAutoArchiveDisabled = true;
        return grp;
    }

    
    /**
* @name CreateProducts
* @description Constructs a list of Product2 records for unit tests
**/
    public static List<Product2> ConstructProducts(Integer cnt){
        //ToDo: Ensure this method returns a list, of size cnt, of uniquely named Product2 records
        //  with all the required fields populated
        //  and IsActive = true
        //  an Initial Inventory set to 10
        //  and iterating through the product family picklist values throughout the list.
        List<Product2> products = new List<Product2>();
        for(Integer i = 1; i<=cnt ; i++){
            Product2 prod = new Product2(Name='Product1'+i, Initial_Inventory__c = 10, isActive=true, family= Constants.PRODUCT_FAMILY.get(math.mod(i,4)).getValue());
            products.add(prod);
        }
        
        return products;
    }
    
    /**
* @name CreatePricebookEntries
* @description Constructs a list of PricebookEntry records for unit tests
**/
    public static List<PriceBookEntry> ConstructPricebookEntries(List<Product2> prods){
        //ToDo: Ensure this method returns a corresponding list of PricebookEntries records
        //  related to the provided Products
        //  with all the required fields populated
        //  and IsActive = true
        //  and belonging to the standard Pricebook
        
        List<PriceBookEntry> entries = new List<PriceBookEntry>();
        for(Product2 prod : prods) {
            PriceBookEntry entry = new PriceBookEntry();
            entry.Pricebook2Id = Constants.STANDARD_PRICEBOOK_ID;
            entry.Product2Id = prod.Id;
            entry.UnitPrice = 100;
            entry.IsActive = true;
            entries.add(entry);
        }
        
        return entries;
    }
 /**
     * @name CreateAccounts
     * @description Constructs a list of Account records for unit tests
    **/
    public static List<Account> ConstructAccounts(Integer cnt){
        //ToDo: Ensure this method returns a list of size cnt of uniquely named Account records
        //  with all of the required fields populated.
        List<Account> testAcc = new List<Account>();
        for(Integer i=1;i<=cnt;i++){
            testAcc.add(new Account(Name='TEST_ACCOUNT_'+i));
        }
        return testAcc;
    }
    
    /**
* @name CreateContacts
* @description Constructs a list of Contacxt records for unit tests
**/
    public static List<Contact> ConstructContacts(Integer cnt, List<Account> accts){
        //ToDo: Ensure this method returns a list, of size cnt, of uniquely named Contact records
        //  related to the provided Accounts
        //  with all of the required fields populated.
        List<Contact> contacts = new List<Contact>();
        for(Integer i=0; i<cnt;i++) {
            Integer index = Math.mod(i, accts.size());
            Contact con = new Contact();
            con.LastName = 'TestContact1'+i;
            con.AccountId = accts.get(index).Id;
            contacts.add(con);
        }
        System.debug('contacts size' + contacts.size());
        System.debug('accts size' + accts.size());
        return contacts;
    }
    
    /**
* @name CreateOrders
* @description Constructs a list of Order records for unit tests
**/
    public static List<Order> ConstructOrders(Integer cnt, List<Account> accts){
        //ToDo: Ensure this method returns a list of size cnt of uniquely named Order records
        //  related to the provided Accounts
        //  with all of the required fields populated.
        List<Order> orders = new List<Order>();
        for (Integer i=0; i <cnt ; i++) {
            Order ord = new Order();
            ord.AccountId = accts.get(math.mod(i, accts.size())).Id;
            ord.Pricebook2Id = Constants.STANDARD_PRICEBOOK_ID;
            ord.Status='Draft';
            ord.EffectiveDate = System.today();
            orders.add(ord);
        }
        return orders;
    }
    
    /**
* @name CreateOrderItems
* @description Constructs a list of OrderItem records for unit tests
**/
    public static  List<OrderItem> ConstructOrderItems(integer cnt, list<pricebookentry> pbes, list<order> ords){
        //ToDo: Ensure this method returns a list of size cnt of OrderItem records
        //  related to the provided Pricebook Entries
        //  and related to the provided Orders
        //  with all of the required fields populated.
        //  Hint: Use the DEFAULT_ROWS constant for Quantity as it will be used in the next challenge
        List<OrderItem> items = new List<OrderItem>();
        for(Integer i = 0; i <cnt; i++) {
            OrderItem ord = new OrderItem();
            ord.PricebookEntryId = pbes.get(math.mod(i, pbes.size())).Id;
            ord.OrderId = ords.get(math.mod(i, ords.size())).Id;
            ord.Quantity = Constants.DEFAULT_ROWS;
            ord.UnitPrice = 250;
            items.add(ord);
        }
        
        return items;
    }
    
    /**
* @name SetupTestData
* @description Inserts accounts, contacts, Products, PricebookEntries, Orders, and OrderItems.
**/
    public static void InsertTestData(Integer cnt){
        //ToDo: Ensure this method calls each of the construct methods
        //  and inserts the results for use as test data.
        CollaborationGroup groups = TestDataFactory.ConstructCollaborationGroup();
        insert groups;
        
        List<Product2>  products= TestDataFactory.ConstructProducts(cnt);
        insert products;
        
        List<PriceBookEntry> entries = TestDataFactory.ConstructPricebookEntries(products);
        insert entries;
        
        List<Account> accts = TestDataFactory.ConstructAccounts(cnt);
        insert accts;
        
        List<Contact> contacts = TestDataFactory.ConstructContacts(cnt,accts);
        insert contacts;
        
        List<Order> orders = TestDataFactory.ConstructOrders( cnt,  accts);
        insert orders;
        
        List<OrderItem> items = TestDataFactory.ConstructOrderItems(cnt, entries, orders);
        insert items;
        
    }
    
    Public static void VerifyQuantityOrdered(Product2 originalProduct, Product2 updatedProduct, Integer qtyOrdered) {
           decimal tot = (originalProduct.Quantity_Ordered__c + qtyOrdered);
        
            system.debug('OldVQ ' + originalProduct.Quantity_Ordered__c);
            system.debug('NewVQ ' + updatedProduct.Quantity_Ordered__c);
            system.debug('QTYVQ ' + qtyOrdered);
        
        system.assertEquals(updatedProduct.Quantity_Ordered__c,tot);     
    }
}


@isTest  (seeAllData=false)
private with sharing class Product2Tests {

    /**
     * @name product2Extension_UnitTest 
     * @description UnitTest for product2Extension
    **/
    @isTest
    private static void Product2Extension_UnitTest(){
// Set-up user
        String uniqueUserName = 'standarduser' + DateTime.now().getTime() + '@testorg.com';
        Profile p = [SELECT Id FROM Profile WHERE Name='Standard User'];
        User u = new User(Alias = 'standt', Email='standarduser@testorg.com',
            EmailEncodingKey='UTF-8', LastName='Testing', LanguageLocaleKey='en_US',
            LocaleSidKey='en_US', ProfileId = p.Id, TimeZoneSidKey='America/Los_Angeles', UserName=uniqueUserName);

        System.runAs(u) {
        
// When a user first visits the page, there should be multiple rows displayed on the screen. 
// Assert that the size of the productsToInsert list is equal to the DEFAULT_ROWS constant.
//        Test.StartTest(); 
            Product2 prod = new Product2(name='Test',isActive=true);
            ApexPages.StandardController stdc = new ApexPages.StandardController(prod);
            Product2Extension p2x = new Product2Extension(stdc);     
            
            System.assert(p2x.productsToInsert.size() == Constants.DEFAULT_ROWS);
//        Test.StopTest();  

// When the Add button is clicked, an additional set of rows should be added, 
// so assert that the size of the productsToInsert ** list is double **DEFAULT_ROWS after the button is clicked once. 
//        Test.StartTest();
            p2x.addRows();
System.assert(p2x.productsToInsert.size() == Constants.DEFAULT_ROWS * 2);
//        Test.StopTest();          

// Next, test the Save button. Verify that populated rows are saved and unpopulated rows are not saved. 
// Loop through the rows in the productsToInsert list and populate the values of the first 5 records, 
// and then simulate clicking the Save button. Verify that the button worked by asserting that only 5 products were saved.
        integer x = 0; 
        for (Product2Extension.ProductWrapper PTI : p2x.productsToInsert){
            pti.productrecord.name='TESTPRODUCT ' + x;
            pti.productRecord.IsActive = true;
            pti.productRecord.Initial_Inventory__c = 20;
            pti.productRecord.Family = Constants.PRODUCT_FAMILY[0].getValue();           
            pti.pricebookEntryRecord.UnitPrice = 10;
            
            x++; if (x==5) {break;}
        }

//        Test.startTest();
            p2x.save();
//        Test.stopTest();
        List<Product2> createdProducts = [SELECT Id FROM Product2];
        System.assertEquals(5, createdProducts.size());

// plus some more test areas        
        p2x.GetFamilyOptions();
        p2x.GetInventory();

    }
    }
}