Index: src/Deltares.DSoilModel.Forms.Tests/ControlTester.cs
===================================================================
diff -u -r343 -r350
--- src/Deltares.DSoilModel.Forms.Tests/ControlTester.cs	(.../ControlTester.cs)	(revision 343)
+++ src/Deltares.DSoilModel.Forms.Tests/ControlTester.cs	(.../ControlTester.cs)	(revision 350)
@@ -13,9 +13,10 @@
 {
     public class ControlTester
     {
-        private readonly string CannotFindControlFormatString = "Cannot find {0} : {1} control.";
         private readonly string InitialValueMismatchString = "Initial value mismatch";
         private readonly string ObjectDidntReceivedValueString = "The object didn't receive the value";
+        private readonly string ClassFieldDoesNotExist = "Cannot find {0} in {1}";
+        private readonly string ClassFieldValueDoesntMatchExpected = "Field {0} has {1} type what is different from {2}";
         private KnownUnits knownUnits;
         private bool oldBypass;
         private LanguageType oldLanguage;
@@ -52,23 +53,28 @@
             LocalizationManager.CurrentLanguage = oldLanguage;
         }
 
-        protected object GetPrivateField(object obj, string field)
+        protected T GetPrivateField<T>(object obj, string field) where T : class
         {
-            return obj.GetType().GetField(field, BindingFlags.NonPublic | BindingFlags.Instance).GetValue(obj);
+            var fi = obj.GetType().GetField(field, BindingFlags.NonPublic | BindingFlags.Instance);
+            Assert.IsNotNull(fi, ClassFieldDoesNotExist, field, obj.GetType().Name);
+            
+            // even if we found the field it class can differ from expected
+            var value = fi.GetValue(obj);
+            Assert.IsInstanceOf(typeof (T), value, ClassFieldValueDoesntMatchExpected, field, value.GetType().Name, typeof(T).Name);
+            return value as T;
         }
 
         private object GetValue<T, T2>(T target, Expression<Func<T, T2>> outExpr)
         {
-            var expr = (MemberExpression)outExpr.Body;
-            var prop = (PropertyInfo)expr.Member;
+            var expr = (MemberExpression) outExpr.Body;
+            var prop = (PropertyInfo) expr.Member;
             return prop.GetValue(target, null);
         }
 
         protected void TestControlVisibleEnabled(IPropertyControl parentControl, string spinEditName, bool isVisibleExpected,
             bool isEnabledExpected)
         {
-            var edit = GetPrivateField(parentControl, spinEditName) as Control;
-            Assert.IsNotNull(edit, CannotFindControlFormatString, spinEditName, "<unknown>");
+            var edit = GetPrivateField<Control>(parentControl, spinEditName);
             Assert.AreEqual(isVisibleExpected, edit.Visible, spinEditName + ": Visible-check failed");
             Assert.AreEqual(isEnabledExpected, edit.Enabled, spinEditName + ": Enabled-check failed");
         }
@@ -78,8 +84,7 @@
             TestControlVisibleEnabled(parentControl, spinEditName, isVisibleExpected, isEnabledExpected);
             if (isVisibleExpected)
             {
-                var edit = GetPrivateField(parentControl, spinEditName) as SpinEdit;
-                Assert.IsNotNull(edit, CannotFindControlFormatString, spinEditName, "SpinEdit");
+                var edit = GetPrivateField<SpinEdit>(parentControl, spinEditName);
 
                 var initialValue = GetValue(target, outExpr);
                 Assert.AreEqual(initialValue, edit.Value, InitialValueMismatchString);
@@ -99,8 +104,7 @@
             TestControlVisibleEnabled(parentControl, textEditName, isVisibleExpected, isEnabledExpected);
             if (isVisibleExpected)
             {
-                var edit = GetPrivateField(parentControl, textEditName) as TextEdit;
-                Assert.IsNotNull(edit, CannotFindControlFormatString, textEditName, "TextEdit");
+                var edit = GetPrivateField<TextEdit>(parentControl, textEditName);
 
                 var initialValue = GetValue(target, outExpr);
                 Assert.AreEqual(initialValue, edit.EditValue, InitialValueMismatchString);
@@ -117,16 +121,14 @@
         protected void TestLabelControlVisibleValue(IPropertyControl parentControl, string labelControlName, bool isVisibleExpected, string labelTextExpected)
         {
             TestControlVisibleEnabled(parentControl, labelControlName, isVisibleExpected, true); // labels are always enabled in DSL projects
-            var labelControl = GetPrivateField(parentControl, labelControlName) as LabelControl;
-            Assert.IsNotNull(labelControl, CannotFindControlFormatString, labelControlName, "LabelControl");
+            var labelControl = GetPrivateField<LabelControl>(parentControl, labelControlName);
             Assert.AreEqual(labelTextExpected, labelControl.Text, InitialValueMismatchString);
         }
 
         protected void TestGridVisibleEnabledSize(IPropertyControl parentControl, string gridName, bool isVisibleExpected, bool isEnabledExpected, int rowCount, int colCount)
         {
             TestControlVisibleEnabled(parentControl, gridName, isVisibleExpected, isEnabledExpected);
-            var gridControl = GetPrivateField(parentControl, gridName) as GridViewControl;
-            Assert.IsNotNull(gridControl, CannotFindControlFormatString, gridName, "GridViewControl");
+            var gridControl = GetPrivateField<GridViewControl>(parentControl, gridName);
             Assert.AreEqual(rowCount, gridControl.gridView1.RowCount, "Row count mismatch");
             Assert.AreEqual(colCount, gridControl.gridView1.Columns.Count, "Columns count mismatch");
         }