Index: DamEngine/trunk/src/Deltares.DamEngine.Calculators.Tests/KernelWrappers/MacroStabilityCommon/MacroStabilityIo/ObjectRegistryTest.cs
===================================================================
diff -u
--- DamEngine/trunk/src/Deltares.DamEngine.Calculators.Tests/KernelWrappers/MacroStabilityCommon/MacroStabilityIo/ObjectRegistryTest.cs	(revision 0)
+++ DamEngine/trunk/src/Deltares.DamEngine.Calculators.Tests/KernelWrappers/MacroStabilityCommon/MacroStabilityIo/ObjectRegistryTest.cs	(revision 6367)
@@ -0,0 +1,98 @@
+// Copyright (C) Stichting Deltares 2024. All rights reserved.
+// 
+// This file is part of the Dam Engine.
+// 
+// The Dam Engine is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+// 
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Affero General Public License for more details.
+// 
+// You should have received a copy of the GNU Affero General Public License
+// along with this program. If not, see <http://www.gnu.org/licenses/>.
+// 
+// All names, logos, and references to "Deltares" are registered trademarks of
+// Stichting Deltares and remain full property of Stichting Deltares at all times.
+// All rights reserved.
+
+using System;
+using Deltares.DamEngine.Calculators.KernelWrappers.MacroStabilityCommon.MacroStabilityIo;
+using NUnit.Framework;
+
+namespace Deltares.DamEngine.Calculators.Tests.KernelWrappers.MacroStabilityCommon.MacroStabilityIo;
+
+[TestFixture]
+public class ObjectRegistryTest
+{
+    [TestFixture]
+    public class GivenObjectRegistry
+    {
+        private static ObjectRegistry objectRegistry;
+
+        [SetUp]
+        public static void Arrange()
+        {
+            objectRegistry = new ObjectRegistry();
+        }
+
+        [Test]
+        public static void WhenGetObjectFromNonExistingIndex_ThenThrowsInvalidOperationException()
+        {
+            Assert.That(() => objectRegistry.GetObject(0), Throws.InstanceOf<InvalidOperationException>());
+        }
+
+        [Test]
+        public static void WhenGetIdWithoutObject_ThenThrowsArgumentNullException()
+        {
+            Assert.That(() => objectRegistry.GetId(null), Throws.ArgumentNullException);
+        }
+
+        [TestFixture]
+        public class WhenGetId : GivenObjectRegistry
+        {
+            private static int index;
+            private static object @object;
+
+            [SetUp]
+            public new static void Arrange()
+            {
+                @object = new object();
+                index = objectRegistry.GetId(@object);
+            }
+
+            [Test]
+            public static void ThenIndexIsZero()
+            {
+                Assert.That(index, Is.Zero);
+            }
+
+            [Test]
+            public static void WhenGetObjectUsingReceivedIndex_ThenObjectIsTheSame()
+            {
+                object receivedObject = objectRegistry.GetObject(index);
+
+                Assert.That(receivedObject, Is.SameAs(@object));
+            }
+
+            [Test]
+            public static void WhenGetIdFromOtherObject_ThenReturnsIndexIncreasedWithOne()
+            {
+                int newIndex = objectRegistry.GetId(new object());
+
+                Assert.That(newIndex, Is.EqualTo(index + 1));
+            }
+
+            [Test]
+            public static void WhenGetIdFromSameObject_ThenReturnsIndex()
+            {
+                int newIndex = objectRegistry.GetId(@object);
+
+                Assert.That(newIndex, Is.EqualTo(index));
+            }
+        }
+    }
+}
\ No newline at end of file
Index: DamEngine/trunk/src/Deltares.DamEngine.Calculators/KernelWrappers/MacroStabilityCommon/MacroStabilityIo/FillMacroStabilityInterfaceInputFromEngine.cs
===================================================================
diff -u -r6361 -r6367
--- DamEngine/trunk/src/Deltares.DamEngine.Calculators/KernelWrappers/MacroStabilityCommon/MacroStabilityIo/FillMacroStabilityInterfaceInputFromEngine.cs	(.../FillMacroStabilityInterfaceInputFromEngine.cs)	(revision 6361)
+++ DamEngine/trunk/src/Deltares.DamEngine.Calculators/KernelWrappers/MacroStabilityCommon/MacroStabilityIo/FillMacroStabilityInterfaceInputFromEngine.cs	(.../FillMacroStabilityInterfaceInputFromEngine.cs)	(revision 6367)
@@ -47,38 +47,6 @@
 
 namespace Deltares.DamEngine.Calculators.KernelWrappers.MacroStabilityCommon.MacroStabilityIo;
 
-internal class ObjectRegistry
-{
-    private readonly ConcurrentDictionary<object, int> objects = new ConcurrentDictionary<object, int>();
-    private int currentId;
-
-    public int GetId(object @object)
-    {
-        AddsObjectToRegistryIfNotExistsInRegistry(@object);
-        return objects[@object];
-    }
-
-    public object GetObject(int id)
-    {
-        return objects.First<KeyValuePair<object, int>>((Func<KeyValuePair<object, int>, bool>) (x => x.Value == id)).Key;
-    }
-
-    private void AddsObjectToRegistryIfNotExistsInRegistry(object @object)
-    {
-        if (IsObjectInRegistry(@object))
-            return;
-        AddObjectToRegistry(@object);
-    }
-
-    private bool IsObjectInRegistry(object @object) => this.objects.ContainsKey(@object);
-
-    private void AddObjectToRegistry(object @object)
-    {
-        objects.AddOrUpdate(@object, currentId, (Func<object, int, int>) ((o, i) => objects.Count + 1));
-        ++currentId;
-    }
-}
-
 public class FillMacroStabilityInterfaceInputFromEngine
 {
     /// <summary>Gets or sets the UpliftVan calculation grid.</summary>
Index: DamEngine/trunk/src/Deltares.DamEngine.Calculators/KernelWrappers/MacroStabilityCommon/MacroStabilityIo/ObjectRegistry.cs
===================================================================
diff -u
--- DamEngine/trunk/src/Deltares.DamEngine.Calculators/KernelWrappers/MacroStabilityCommon/MacroStabilityIo/ObjectRegistry.cs	(revision 0)
+++ DamEngine/trunk/src/Deltares.DamEngine.Calculators/KernelWrappers/MacroStabilityCommon/MacroStabilityIo/ObjectRegistry.cs	(revision 6367)
@@ -0,0 +1,75 @@
+// Copyright (C) Stichting Deltares 2024. All rights reserved.
+// 
+// This file is part of the Dam Engine.
+// 
+// The Dam Engine is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+// 
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Affero General Public License for more details.
+// 
+// You should have received a copy of the GNU Affero General Public License
+// along with this program. If not, see <http://www.gnu.org/licenses/>.
+// 
+// All names, logos, and references to "Deltares" are registered trademarks of
+// Stichting Deltares and remain full property of Stichting Deltares at all times.
+// All rights reserved.
+
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Deltares.DamEngine.Calculators.KernelWrappers.MacroStabilityCommon.MacroStabilityIo;
+
+/// <summary>
+/// Class providing methods to register objects.
+/// </summary>
+internal class ObjectRegistry
+{
+    private readonly ConcurrentDictionary<object, int> objects = new ConcurrentDictionary<object, int>();
+    private int currentId;
+
+    /// <summary>
+    /// <summary>Gets an unique id of an object based on its instance.</summary>
+    /// </summary>
+    /// <param name="object">The object to get the id from.</param>
+    /// <returns>The id.</returns>
+    /// <exception cref="ArgumentNullException">Thrown when <paramref name="object"/> is <c>null</c>.</exception>
+    public int GetId(object @object)
+    {
+        AddsObjectToRegistryIfNotExistsInRegistry(@object);
+        return objects[@object];
+    }
+
+    /// <summary>
+    /// <summary>Gets an object from an id.</summary>
+    /// </summary>
+    /// <param name="id">The id to get the object from.</param>
+    /// <returns>The object of <c>null</c> if not exists.</returns>
+    /// <exception cref="InvalidOperationException">Thrown when <paramref name="id"/> is not valid.</exception>
+    public object GetObject(int id)
+    {
+        return objects.First<KeyValuePair<object, int>>((Func<KeyValuePair<object, int>, bool>) (x => x.Value == id)).Key;
+    }
+
+    private void AddsObjectToRegistryIfNotExistsInRegistry(object @object)
+    {
+        if (IsObjectInRegistry(@object))
+            return;
+        AddObjectToRegistry(@object);
+    }
+
+    private bool IsObjectInRegistry(object @object) => this.objects.ContainsKey(@object);
+
+    private void AddObjectToRegistry(object @object)
+    {
+        objects.AddOrUpdate(@object, currentId, (Func<object, int, int>) ((o, i) => objects.Count + 1));
+        ++currentId;
+    }
+}
+