Fix PrefetchManagerBasic.ReferenceToSessionIsNotPreservedInCacheTest

Author: AlexUstinov

Orm/Xtensive.Orm.Tests/Storage/Prefetch/PrefetchManagerBasicTest.cs

@@ -7,6 +7,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Threading;
 using NUnit.Framework;
 using Xtensive.Core;
 using Xtensive.Collections;
@@ -931,6 +932,15 @@ public void RemoveTest()
 
     [Test]
     public void ReferenceToSessionIsNotPreservedInCacheTest()
+    {
+      // Use separate method for session related processing
+      // to make sure we don't hold session reference somewhere on stack
+      OpenSessionsAndRunPrefetches();
+      TestHelper.CollectGarbage(true);
+      Assert.That(instanceCount, Is.EqualTo(0));
+    }
+
+    private void OpenSessionsAndRunPrefetches()
     {
       instanceCount = 10;
       for (int i = 0; i < instanceCount; i++) {
@@ -948,8 +958,6 @@ public void ReferenceToSessionIsNotPreservedInCacheTest()
           t.Complete();
         }
       }
-      TestHelper.CollectGarbage(true);
-      Assert.That(instanceCount, Is.EqualTo(0));
     }
 
     private void PrefetchIntrinsicFields(PrefetchManager prefetchManager, Key key, Type type)