ExpressionSessionLeakTest: Add failing test for NH-3579.

Author: oskarb

src/NHibernate.Test/Linq/ExpressionSessionLeakTest.cs

@@ -0,0 +1,39 @@
+using System;
+using System.Linq;
+using NHibernate.DomainModel.Northwind.Entities;
+using NHibernate.Linq;
+using NUnit.Framework;
+
+namespace NHibernate.Test.Linq
+{
+	public class ExpressionSessionLeakTest : LinqTestCase
+	{
+		[Test]
+		[Ignore("Not fixed yet. NH-3579")]
+		public void SessionGetsCollected()
+		{
+			var reference = DoLinqInSeparateSession();
+
+			GC.Collect();
+
+			Assert.Null(reference.Target);
+		}
+
+
+		private WeakReference DoLinqInSeparateSession()
+		{
+			var leakTest = session.SessionFactory.OpenSession();
+
+			// It appears linq expressions will (or might) contain a reference to the
+			// IQueryable. At time of writing, linq expressions are helt within NhLinqExpression,
+			// which in turn will be held in the query plan cache. Since the IQueryable will
+			// be an NhQueryable, which holds a reference to the SessionImpl instance,
+			// we will be leaking session instances.
+
+			var query = leakTest.Query<Customer>().FirstOrDefault(t => t.CustomerId != "");
+			leakTest.Dispose();
+
+			return new WeakReference(leakTest, false);
+		}
+	}
+}

src/NHibernate.Test/NHibernate.Test.csproj

@@ -513,6 +513,7 @@
     <Compile Include="Linq\CasingTest.cs" />
     <Compile Include="Linq\CharComparisonTests.cs" />
     <Compile Include="Linq\DateTimeTests.cs" />
+    <Compile Include="Linq\ExpressionSessionLeakTest.cs" />
     <Compile Include="Linq\LoggingTests.cs" />
     <Compile Include="Linq\QueryTimeoutTests.cs" />
     <Compile Include="Linq\JoinTests.cs" />