Adding additional unit tests (#406)

* Creating new test class for RemoveEmptyItems

* Adding tests for AddItemToBasket in BasketService

* Removing unused GetBasketItemCountAsync

* Adding tests for BasketWithItemsSpecification

* Adding CustomerORdersWithItemsSpecification tests

* Adding CatalogFilterPaginatedSpecifciation tests

* Adding CatalogItemsSpecification tests

src/ApplicationCore/Specifications/BasketWithItemsSpecification.cs

@@ -9,6 +9,7 @@ namespace Microsoft.eShopWeb.ApplicationCore.Specifications
         {
             AddInclude(b => b.Items);
         }
+
         public BasketWithItemsSpecification(string buyerId) : base(b => b.BuyerId == buyerId)
         {
             AddInclude(b => b.Items);