NH-3797 - Added test cases

Author: PleasantD

src/NHibernate.Test/Linq/ByMethod/GroupByTests.cs

@@ -520,6 +520,27 @@ into grp
 			Assert.That(result.Count, Is.EqualTo(77));
 		}
 
+        [Test(Description = "NH-3797")]
+        public void GroupByComputedValue()
+        {
+            var orderGroups = db.Orders.GroupBy(o => o.Customer.CustomerId == null ? 0 : 1).Select(g => new { Key = g.Key, Count = g.Count() }).ToList();
+            Assert.AreEqual(830, orderGroups.Sum(g => g.Count));
+        }
+
+        [Test(Description = "NH-3797")]
+        public void GroupByComputedValueInAnonymousType()
+        {
+            var orderGroups = db.Orders.GroupBy(o => new { Key = o.Customer.CustomerId == null ? 0 : 1 }).Select(g => new { Key = g.Key, Count = g.Count() }).ToList();
+            Assert.AreEqual(830, orderGroups.Sum(g => g.Count));
+        }
+
+        [Test(Description = "NH-3797")]
+        public void GroupByComputedValueInObjectArray()
+        {
+            var orderGroups = db.Orders.GroupBy(o => new[] { o.Customer.CustomerId == null ? 0 : 1, }).Select(g => new { Key = g.Key, Count = g.Count() }).ToList();
+            Assert.AreEqual(830, orderGroups.Sum(g => g.Count));
+        }
+
 		private static void CheckGrouping<TKey, TElement>(IEnumerable<IGrouping<TKey, TElement>> groupedItems, Func<TElement, TKey> groupBy)
 		{
 			var used = new HashSet<object>();