Fix #167 #179 #185 #187

SysML2.NET.Tests/Extend/ReferenceSubsettingExtensionsTestFixture.cs

@@ -1,7 +1,7 @@
-// -------------------------------------------------------------------------------------------------
+// -------------------------------------------------------------------------------------------------
 // <copyright file="ReferenceSubsettingExtensionsTestFixture.cs" company="Starion Group S.A.">
 // 
-//   Copyright 2022-2026 Starion Group S.A.
+//   Copyright (C) 2022-2026 Starion Group S.A.
 // 
 //   Licensed under the Apache License, Version 2.0 (the "License");
 //   you may not use this file except in compliance with the License.
@@ -21,18 +21,43 @@
 namespace SysML2.NET.Tests.Extend
 {
     using System;
-    
+
     using NUnit.Framework;
-    
+
     using SysML2.NET.Core.POCO.Core.Features;
+    using SysML2.NET.Core.POCO.Root.Elements;
+    using SysML2.NET.Core.POCO.Root.Namespaces;
+    using SysML2.NET.Exceptions;
 
     [TestFixture]
     public class ReferenceSubsettingExtensionsTestFixture
     {
         [Test]
-        public void ComputeReferencingFeature_ThrowsNotSupportedException()
+        public void VerifyComputeReferencingFeature()
         {
-            Assert.That(() => ((IReferenceSubsetting)null).ComputeReferencingFeature(), Throws.TypeOf<NotSupportedException>());
+            // Null subject → ArgumentNullException.
+            Assert.That(() => ((IReferenceSubsetting)null).ComputeReferencingFeature(), Throws.TypeOf<ArgumentNullException>());
+
+            // Empty ReferenceSubsetting (OwningRelatedElement is null) → [1..1] violation: IncompleteModelException.
+            var emptySubsetting = new ReferenceSubsetting();
+
+            Assert.That(() => emptySubsetting.ComputeReferencingFeature(), Throws.TypeOf<IncompleteModelException>());
+
+            // OwningRelatedElement is an IFeature → returns the same instance.
+            var feature = new Feature();
+            var refSubsettingWithFeature = new ReferenceSubsetting();
+
+            ((IContainedRelationship)refSubsettingWithFeature).OwningRelatedElement = feature;
+
+            Assert.That(refSubsettingWithFeature.ComputeReferencingFeature(), Is.SameAs(feature));
+
+            // OwningRelatedElement is a non-IFeature (Namespace) → [1..1] type violation: IncompleteModelException.
+            var namespaceObj = new Namespace();
+            var refSubsettingWithNamespace = new ReferenceSubsetting();
+
+            ((IContainedRelationship)refSubsettingWithNamespace).OwningRelatedElement = namespaceObj;
+
+            Assert.That(() => refSubsettingWithNamespace.ComputeReferencingFeature(), Throws.TypeOf<IncompleteModelException>());
         }
     }
 }

SysML2.NET.Tests/Extend/SpecializationExtensionsTestFixture.cs

@@ -1,7 +1,7 @@
-// -------------------------------------------------------------------------------------------------
+// -------------------------------------------------------------------------------------------------
 // <copyright file="SpecializationExtensionsTestFixture.cs" company="Starion Group S.A.">
 // 
-//   Copyright 2022-2026 Starion Group S.A.
+//   Copyright (C) 2022-2026 Starion Group S.A.
 // 
 //   Licensed under the Apache License, Version 2.0 (the "License");
 //   you may not use this file except in compliance with the License.
@@ -21,18 +21,45 @@
 namespace SysML2.NET.Tests.Extend
 {
     using System;
-    
+
     using NUnit.Framework;
-    
+
     using SysML2.NET.Core.POCO.Core.Types;
+    using SysML2.NET.Core.POCO.Root.Elements;
+    using SysML2.NET.Core.POCO.Root.Namespaces;
+    using SysML2.NET.Extensions;
+
+    using Type = SysML2.NET.Core.POCO.Core.Types.Type;
 
     [TestFixture]
     public class SpecializationExtensionsTestFixture
     {
         [Test]
-        public void ComputeOwningType_ThrowsNotSupportedException()
+        public void VerifyComputeOwningType()
         {
-            Assert.That(() => ((ISpecialization)null).ComputeOwningType(), Throws.TypeOf<NotSupportedException>());
+            Assert.That(() => ((ISpecialization)null).ComputeOwningType(), Throws.TypeOf<ArgumentNullException>());
+
+            var emptySpecialization = new Specialization();
+
+            Assert.That(emptySpecialization.ComputeOwningType(), Is.Null);
+
+            var owningType = new Type();
+            var specialization = new Specialization();
+
+            owningType.AssignOwnership(specialization);
+
+            Assert.That(specialization.ComputeOwningType(), Is.SameAs(owningType));
+
+            // NOTE: assigning a non-IType as OwningRelatedElement is not guarded by the public
+            // AssignOwnership API for Specialization, so we directly set the backing field via
+            // the IContainedRelationship explicit interface to exercise the as-cast-returns-null
+            // path, which proves ComputeOwningType returns null when the owner is not an IType.
+            var nonTypeSpecialization = new Specialization();
+            var nonTypeOwner = new Namespace();
+
+            ((IContainedRelationship)nonTypeSpecialization).OwningRelatedElement = nonTypeOwner;
+
+            Assert.That(nonTypeSpecialization.ComputeOwningType(), Is.Null);
         }
     }
 }

SysML2.NET.Tests/Extend/SubclassificationExtensionsTestFixture.cs

@@ -1,7 +1,7 @@
-// -------------------------------------------------------------------------------------------------
+// -------------------------------------------------------------------------------------------------
 // <copyright file="SubclassificationExtensionsTestFixture.cs" company="Starion Group S.A.">
 // 
-//   Copyright 2022-2026 Starion Group S.A.
+//   Copyright (C) 2022-2026 Starion Group S.A.
 // 
 //   Licensed under the Apache License, Version 2.0 (the "License");
 //   you may not use this file except in compliance with the License.
@@ -21,18 +21,40 @@
 namespace SysML2.NET.Tests.Extend
 {
     using System;
-    
+
     using NUnit.Framework;
-    
+
     using SysML2.NET.Core.POCO.Core.Classifiers;
+    using SysML2.NET.Core.POCO.Root.Elements;
+    using SysML2.NET.Core.POCO.Root.Namespaces;
 
     [TestFixture]
     public class SubclassificationExtensionsTestFixture
     {
         [Test]
-        public void ComputeOwningClassifier_ThrowsNotSupportedException()
+        public void VerifyComputeOwningClassifier()
         {
-            Assert.That(() => ((ISubclassification)null).ComputeOwningClassifier(), Throws.TypeOf<NotSupportedException>());
+            Assert.That(() => ((ISubclassification)null).ComputeOwningClassifier(), Throws.TypeOf<ArgumentNullException>());
+
+            // Empty Subclassification (OwningRelatedElement is null) → returns null.
+            var subclassification = new Subclassification();
+
+            Assert.That(subclassification.ComputeOwningClassifier(), Is.Null);
+
+            // OwningRelatedElement is an IClassifier → returns the classifier.
+            var classifier = new Classifier();
+
+            ((IContainedRelationship)subclassification).OwningRelatedElement = classifier;
+
+            Assert.That(subclassification.ComputeOwningClassifier(), Is.SameAs(classifier));
+
+            // OwningRelatedElement is NOT an IClassifier (e.g. Namespace) → returns null.
+            var nonClassifierSubclassification = new Subclassification();
+            var namespaceObj = new Namespace();
+
+            ((IContainedRelationship)nonClassifierSubclassification).OwningRelatedElement = namespaceObj;
+
+            Assert.That(nonClassifierSubclassification.ComputeOwningClassifier(), Is.Null);
         }
     }
 }

SysML2.NET.Tests/Extend/SubsettingExtensionsTestFixture.cs

@@ -1,7 +1,7 @@
-// -------------------------------------------------------------------------------------------------
+// -------------------------------------------------------------------------------------------------
 // <copyright file="SubsettingExtensionsTestFixture.cs" company="Starion Group S.A.">
 // 
-//   Copyright 2022-2026 Starion Group S.A.
+//   Copyright (C) 2022-2026 Starion Group S.A.
 // 
 //   Licensed under the Apache License, Version 2.0 (the "License");
 //   you may not use this file except in compliance with the License.
@@ -21,18 +21,37 @@
 namespace SysML2.NET.Tests.Extend
 {
     using System;
-    
+
     using NUnit.Framework;
 
     using SysML2.NET.Core.POCO.Core.Features;
-
+    using SysML2.NET.Core.POCO.Root.Elements;
+    using SysML2.NET.Core.POCO.Root.Namespaces;
+
     [TestFixture]
     public class SubsettingExtensionsTestFixture
     {
         [Test]
-        public void ComputeOwningFeature_ThrowsNotSupportedException()
+        public void VerifyComputeOwningFeature()
         {
-            Assert.That(() => ((ISubsetting)null).ComputeOwningFeature(), Throws.TypeOf<NotSupportedException>());
+            Assert.That(() => ((ISubsetting)null).ComputeOwningFeature(), Throws.TypeOf<ArgumentNullException>());
+
+            var subsetting = new Subsetting();
+
+            Assert.That(subsetting.ComputeOwningFeature(), Is.Null);
+
+            var feature = new Feature();
+
+            ((IContainedRelationship)subsetting).OwningRelatedElement = feature;
+
+            Assert.That(subsetting.ComputeOwningFeature(), Is.SameAs(feature));
+
+            var namespaceOwner = new Namespace();
+            var nonFeatureSubsetting = new Subsetting();
+
+            ((IContainedRelationship)nonFeatureSubsetting).OwningRelatedElement = namespaceOwner;
+
+            Assert.That(nonFeatureSubsetting.ComputeOwningFeature(), Is.Null);
         }
     }
 }

SysML2.NET.sln.DotSettings

@@ -3,7 +3,7 @@
 	<s:String x:Key="/Default/CodeStyle/FileHeader/FileHeaderText/@EntryValue">-------------------------------------------------------------------------------------------------&#xD;
 &lt;copyright file="${File.FileName}" company="Starion Group S.A."&gt;&#xD;
 &#xD;
-  Copyright 2022-2026 Starion Group S.A.&#xD;
+  Copyright (C) 2022-2026 Starion Group S.A.&#xD;
 &#xD;
   Licensed under the Apache License, Version 2.0 (the "License");&#xD;
   you may not use this file except in compliance with the License.&#xD;

SysML2.NET/Extend/ReferenceSubsettingExtensions.cs

@@ -1,53 +1,61 @@
 // -------------------------------------------------------------------------------------------------
 // <copyright file="ReferenceSubsettingExtensions.cs" company="Starion Group S.A.">
-//
-//    Copyright (C) 2022-2026 Starion Group S.A.
-//
-//    Licensed under the Apache License, Version 2.0 (the "License");
-//    you may not use this file except in compliance with the License.
-//    You may obtain a copy of the License at
-//
+// 
+//   Copyright (C) 2022-2026 Starion Group S.A.
+// 
+//   Licensed under the Apache License, Version 2.0 (the "License");
+//   you may not use this file except in compliance with the License.
+//   You may obtain a copy of the License at
+// 
 //        http://www.apache.org/licenses/LICENSE-2.0
-//
+// 
 //    Unless required by applicable law or agreed to in writing, software
 //    distributed under the License is distributed on an "AS IS" BASIS,
 //    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 //    See the License for the specific language governing permissions and
 //    limitations under the License.
-//
+// 
 // </copyright>
 // ------------------------------------------------------------------------------------------------
 
 namespace SysML2.NET.Core.POCO.Core.Features
 {
     using System;
-    using System.Collections.Generic;
 
-    using SysML2.NET.Core.POCO.Core.Types;
-    using SysML2.NET.Core.POCO.Root.Annotations;
-    using SysML2.NET.Core.POCO.Root.Elements;
-    using SysML2.NET.Core.POCO.Root.Namespaces;
+    using SysML2.NET.Exceptions;
 
     /// <summary>
-    /// The <see cref="ReferenceSubsettingExtensions"/> class provides extensions methods for
-    /// the <see cref="IReferenceSubsetting"/> interface
+    /// The <see cref="ReferenceSubsettingExtensions" /> class provides extensions methods for
+    /// the <see cref="IReferenceSubsetting" /> interface
     /// </summary>
     internal static class ReferenceSubsettingExtensions
     {
         /// <summary>
-        /// Computes the derived property.
+        /// Computes the derived property <c>referencingFeature</c> — the <see cref="IFeature" /> that owns
+        /// this <see cref="IReferenceSubsetting" /> relationship, which is also its subsettingFeature.
         /// </summary>
         /// <param name="referenceSubsettingSubject">
-        /// The subject <see cref="IReferenceSubsetting"/>
+        /// The subject <see cref="IReferenceSubsetting" />
         /// </param>
         /// <returns>
-        /// the computed result
+        /// The <see cref="IFeature" /> that is the owning related element of this relationship.
         /// </returns>
-        [System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
+        /// <exception cref="ArgumentNullException">
+        /// Thrown when <paramref name="referenceSubsettingSubject" /> is null.
+        /// </exception>
+        /// <exception cref="IncompleteModelException">
+        /// Thrown when the owning related element is null or is not an <see cref="IFeature" />.
+        /// </exception>
         internal static IFeature ComputeReferencingFeature(this IReferenceSubsetting referenceSubsettingSubject)
         {
-            throw new NotSupportedException("Create a GitHub issue when this method is required");
-        }
+            if (referenceSubsettingSubject == null)
+            {
+                throw new ArgumentNullException(nameof(referenceSubsettingSubject));
+            }
 
+            return referenceSubsettingSubject.OwningRelatedElement as IFeature
+                   ?? throw new IncompleteModelException(
+                       $"{nameof(referenceSubsettingSubject)} must have an owning related element of type {nameof(IFeature)}");
+        }
     }
 }

SysML2.NET/Extend/SpecializationExtensions.cs

@@ -1,52 +1,47 @@
 // -------------------------------------------------------------------------------------------------
 // <copyright file="SpecializationExtensions.cs" company="Starion Group S.A.">
-//
-//    Copyright (C) 2022-2026 Starion Group S.A.
-//
-//    Licensed under the Apache License, Version 2.0 (the "License");
-//    you may not use this file except in compliance with the License.
-//    You may obtain a copy of the License at
-//
+// 
+//   Copyright (C) 2022-2026 Starion Group S.A.
+// 
+//   Licensed under the Apache License, Version 2.0 (the "License");
+//   you may not use this file except in compliance with the License.
+//   You may obtain a copy of the License at
+// 
 //        http://www.apache.org/licenses/LICENSE-2.0
-//
+// 
 //    Unless required by applicable law or agreed to in writing, software
 //    distributed under the License is distributed on an "AS IS" BASIS,
 //    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 //    See the License for the specific language governing permissions and
 //    limitations under the License.
-//
+// 
 // </copyright>
 // ------------------------------------------------------------------------------------------------
 
 namespace SysML2.NET.Core.POCO.Core.Types
 {
     using System;
-    using System.Collections.Generic;
-
-    using SysML2.NET.Core.POCO.Root.Annotations;
-    using SysML2.NET.Core.POCO.Root.Elements;
-    using SysML2.NET.Core.POCO.Root.Namespaces;
 
     /// <summary>
-    /// The <see cref="SpecializationExtensions"/> class provides extensions methods for
-    /// the <see cref="ISpecialization"/> interface
+    /// The <see cref="SpecializationExtensions" /> class provides extensions methods for
+    /// the <see cref="ISpecialization" /> interface
     /// </summary>
     internal static class SpecializationExtensions
     {
         /// <summary>
         /// Computes the derived property.
         /// </summary>
         /// <param name="specializationSubject">
-        /// The subject <see cref="ISpecialization"/>
+        /// The subject <see cref="ISpecialization" />
         /// </param>
         /// <returns>
         /// the computed result
         /// </returns>
-        [System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
         internal static IType ComputeOwningType(this ISpecialization specializationSubject)
         {
-            throw new NotSupportedException("Create a GitHub issue when this method is required");
+            return specializationSubject == null
+                ? throw new ArgumentNullException(nameof(specializationSubject))
+                : specializationSubject.OwningRelatedElement as IType;
         }
-
     }
 }