Added unit test for failing delete statement

src/NHibernate.Test/NHSpecificTest/GH2688/BasketItem.cs

@@ -0,0 +1,41 @@
+using NHibernate.Mapping.ByCode;
+using NHibernate.Mapping.ByCode.Conformist;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace NHibernate.Test.NHSpecificTest.GH2688
+{
+    public class BasketItem
+    {
+        public virtual int Id { get; set; }
+
+        public virtual string Name { get; set; }
+
+        public virtual decimal Price { get; set; }
+
+        public virtual Product Product { get; set; }
+
+		public virtual int OrderBy { get; set; }
+	}
+
+    public class BasketItemMap : ClassMapping<BasketItem>
+    {
+        public BasketItemMap()
+        {
+            Id(x => x.Id, m => {
+                m.Generator(Generators.Identity);
+                m.Column("BasketItemId");
+            });
+            Property(x => x.Name);
+            Property(x => x.Price);
+			Property(x => x.OrderBy);
+            ManyToOne(x => x.Product, m => {
+                m.NotFound(NotFoundMode.Ignore);
+                m.Column("ProductId");
+            });
+        }
+    }
+}

src/NHibernate.Test/NHSpecificTest/GH2688/FixtureByCode.cs

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+using System.Linq;
+using NHibernate.Cfg.MappingSchema;
+using NHibernate.Mapping.ByCode;
+using NUnit.Framework;
+
+namespace NHibernate.Test.NHSpecificTest.GH2688
+{
+	/// <summary>
+	/// Fixture using 'by code' mappings
+	/// </summary>
+	/// <remarks>
+	/// This fixture is identical to <see cref="Fixture" /> except the <see cref="Entity" /> mapping is performed 
+	/// by code in the GetMappings method, and does not require the <c>Mappings.hbm.xml</c> file. Use this approach
+	/// if you prefer.
+	/// </remarks>
+	[TestFixture]
+	public class ByCodeFixture : TestCaseMappingByCode
+	{
+		protected override HbmMapping GetMappings()
+		{
+			var mapper = new ModelMapper();
+			mapper.AddMapping<BasketItemMap>();
+			mapper.AddMapping<ProductMap>();
+			return mapper.CompileMappingForAllExplicitlyAddedEntities();
+		}
+
+		protected override void OnSetUp()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				var e1 = new Product { Name = "Printer Paper", Price = 10 };
+				session.Save(e1);
+
+				var e2 = new BasketItem { Name = "Printer Paper", Price = 10, Product = e1, OrderBy = 1 };
+				session.Save(e2);
+
+				var e3 = new BasketItem { Name = "Cable", Price = 10, Product = null, OrderBy = 2 };
+				session.Save(e3);
+
+				transaction.Commit();
+			}
+		}
+
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				// The HQL delete does all the job inside the database without loading the entities, but it does
+				// not handle delete order for avoiding violating constraints if any. Use
+				// session.Delete("from System.Object");
+				// instead if in need of having NHbernate ordering the deletes, but this will cause
+				// loading the entities in the session.
+				session.CreateQuery("delete from System.Object").ExecuteUpdate();
+
+				transaction.Commit();
+			}
+		}
+
+		[Test]
+		public void YourTestName()
+		{
+			int productId = 0;
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				var product = session.QueryOver<Product>()
+					.Where(p => p.Name == "Printer Paper")
+					.SingleOrDefault();
+				productId = product.Id;
+				session.Delete(product);
+				transaction.Commit();
+			}
+
+			Assert.DoesNotThrow(() => { DeleteBasketItems(productId); });
+		}
+
+		private void DeleteBasketItems(int productId)
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				session.CreateQuery("delete from BasketItem where Product.Id = " + productId)
+					.ExecuteUpdate();
+				transaction.Commit();
+			}
+		}
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH2688/Product.cs

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+using NHibernate;
+using NHibernate.Mapping;
+using NHibernate.Mapping.ByCode;
+using NHibernate.Mapping.ByCode.Conformist;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace NHibernate.Test.NHSpecificTest.GH2688
+{
+    public class Product
+    {
+        public virtual int Id { get; set; }
+
+        public virtual string Name { get; set; }
+
+        public virtual decimal Price { get; set; }
+
+        public virtual IList<BasketItem> BasketItems { get; set; }
+    }
+
+    public class ProductMap : ClassMapping<Product>
+    {
+        public ProductMap()
+        {
+            Id(x => x.Id, m => {
+                m.Generator(Generators.Identity);
+                m.Column("ProductId");
+            });
+            Property(x => x.Name);
+            Property(x => x.Price);
+            Bag(x => x.BasketItems, bag => {
+                bag.Inverse(true);
+                bag.Lazy(CollectionLazy.Lazy);
+                bag.Cascade(Mapping.ByCode.Cascade.Persist);
+				bag.OrderBy("OrderBy asc");
+                bag.Key(km =>
+                {
+                    km.Column("ProductId");
+                    km.ForeignKey("none");
+                });
+            }, a => a.OneToMany());
+        }
+    }
+}