Index: src/Deltares.DSoilModel.Forms.Tests/ControlTester.cs
===================================================================
diff -u -r371 -r376
--- src/Deltares.DSoilModel.Forms.Tests/ControlTester.cs	(.../ControlTester.cs)	(revision 371)
+++ src/Deltares.DSoilModel.Forms.Tests/ControlTester.cs	(.../ControlTester.cs)	(revision 376)
@@ -2,6 +2,7 @@
 using System.Linq.Expressions;
 using System.Reflection;
 using System.Windows.Forms;
+using Deltares.Standard.Attributes;
 using Deltares.Standard.Forms;
 using Deltares.Standard.Forms.DExpress;
 using Deltares.Standard.Language;
@@ -71,6 +72,13 @@
             return prop.GetValue(target, null);
         }
 
+        private bool IsReadOnly<T, T2>(T target, Expression<Func<T, T2>> outExpr)
+        {
+            var expr = (MemberExpression)outExpr.Body;
+            var prop = (PropertyInfo)expr.Member;
+            return !prop.CanWrite || prop.IsReadOnly();
+        }
+
         protected void TestControlVisibleEnabled(IPropertyControl parentControl, string spinEditName, bool isVisibleExpected,
             bool isEnabledExpected)
         {
@@ -79,7 +87,7 @@
             Assert.AreEqual(isEnabledExpected, edit.Enabled, spinEditName + ": Enabled-check failed");
         }
 
-        protected void TestSpinEditVisibleEnabledValue<T>(IPropertyControl parentControl, string spinEditName, bool isVisibleExpected, bool isEnabledExpected, T target, Expression<Func<T, double>> outExpr, double? valueToTestWith = null)
+        protected void TestSpinEditVisibleEnabledValue<T, TValue>(IPropertyControl parentControl, string spinEditName, bool isVisibleExpected, bool isEnabledExpected, T target, Expression<Func<T, TValue>> outExpr, TValue valueToTestWith = default(TValue))
         {
             TestControlVisibleEnabled(parentControl, spinEditName, isVisibleExpected, isEnabledExpected);
             if (isVisibleExpected)
@@ -89,7 +97,7 @@
                 var initialValue = GetValue(target, outExpr);
                 Assert.AreEqual(initialValue, edit.EditValue, InitialValueMismatchString);
 
-                if (valueToTestWith != null)
+                if (!IsReadOnly(target, outExpr))
                 {
                     edit.EditValue = valueToTestWith;
                     Assert.AreEqual(valueToTestWith, GetValue(target, outExpr), ObjectDidntReceivedValueString);