diff --git a/SysML2.NET.Tests/Extend/ImportExtensionsTestFixture.cs b/SysML2.NET.Tests/Extend/ImportExtensionsTestFixture.cs
index b3e794bb..8b1fceba 100644
--- a/SysML2.NET.Tests/Extend/ImportExtensionsTestFixture.cs
+++ b/SysML2.NET.Tests/Extend/ImportExtensionsTestFixture.cs
@@ -1,44 +1,124 @@
-// -------------------------------------------------------------------------------------------------
+// -------------------------------------------------------------------------------------------------
 // <copyright file="ImportExtensionsTestFixture.cs" company="Starion Group S.A.">
-// 
+//
 //   Copyright 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.Tests.Extend
 {
     using System;
-    
+
+    using Moq;
+
     using NUnit.Framework;
-    
+
     using SysML2.NET.Core.POCO.Root.Namespaces;
+    using SysML2.NET.Extensions;
+
+    using IElement = SysML2.NET.Core.POCO.Root.Elements.IElement;
 
     [TestFixture]
     public class ImportExtensionsTestFixture
     {
         [Test]
-        public void ComputeImportedElement_ThrowsNotSupportedException()
+        public void VerifyComputeImportedElement()
         {
-            Assert.That(() => ((IImport)null).ComputeImportedElement(), Throws.TypeOf<NotSupportedException>());
+            Assert.That(() => ((IImport)null).ComputeImportedElement(), Throws.TypeOf<ArgumentNullException>());
+
+            // Wildcard arm: an IImport that is neither an INamespaceImport nor an IMembershipImport
+            // returns null. Use Moq because IImport is abstract and has no concrete non-subtype POCO.
+            var abstractImport = new Mock<IImport>().Object;
+
+            Assert.That(abstractImport.ComputeImportedElement(), Is.Null);
+
+            // INamespaceImport arm: returns the ImportedNamespace.
+            var importedNamespace = new Namespace();
+            var namespaceImport = new NamespaceImport { ImportedNamespace = importedNamespace };
+
+            Assert.That(namespaceImport.ComputeImportedElement(), Is.SameAs(importedNamespace));
+
+            // INamespaceImport with no ImportedNamespace set → null.
+            var emptyNamespaceImport = new NamespaceImport();
+
+            Assert.That(emptyNamespaceImport.ComputeImportedElement(), Is.Null);
+
+            // IMembershipImport arm: returns the ImportedMembership.MemberElement.
+            var ownerNamespace = new Namespace();
+            var memberElement = new Namespace();
+            var importedMembership = new OwningMembership();
+            ownerNamespace.AssignOwnership(importedMembership, memberElement);
+
+            var membershipImport = new MembershipImport { ImportedMembership = importedMembership };
+
+            Assert.That(membershipImport.ComputeImportedElement(), Is.SameAs(memberElement));
+
+            // IMembershipImport with no ImportedMembership set → null (null-conditional propagates).
+            var emptyMembershipImport = new MembershipImport();
+
+            Assert.That(emptyMembershipImport.ComputeImportedElement(), Is.Null);
+
+            // IMembershipImport whose ImportedMembership has a null MemberElement → null.
+            // A real OwningMembership with zero OwnedRelatedElement throws IncompleteModelException
+            // from ComputeOwnedMemberElement's invariant guard, so use a Moq'd IMembership to
+            // produce a null MemberElement directly without violating the model invariant.
+            var nullMemberMembership = new Mock<IMembership>();
+            nullMemberMembership.SetupGet(membership => membership.MemberElement).Returns((IElement)null);
+            var membershipImportNoMember = new MembershipImport { ImportedMembership = nullMemberMembership.Object };
+
+            Assert.That(membershipImportNoMember.ComputeImportedElement(), Is.Null);
         }
-        
+
         [Test]
-        public void ComputeImportOwningNamespace_ThrowsArgumentNullException()
+        public void VerifyComputeImportOwningNamespace()
         {
             Assert.That(() => ((IImport)null).ComputeImportOwningNamespace(), Throws.TypeOf<ArgumentNullException>());
+
+            // No owner wired → null.
+            var orphanImport = new NamespaceImport();
+
+            Assert.That(orphanImport.ComputeImportOwningNamespace(), Is.Null);
+
+            // Owner wired via AssignOwnership → returns the owning namespace.
+            var owningNamespace = new Namespace();
+            var ownedImport = new NamespaceImport();
+            owningNamespace.AssignOwnership(ownedImport);
+
+            Assert.That(ownedImport.ComputeImportOwningNamespace(), Is.SameAs(owningNamespace));
+        }
+
+        [Test]
+        public void VerifyComputeImportedMembershipsOperation()
+        {
+            // Import.importedMemberships is abstract in the UML; both concrete subclasses
+            // (NamespaceImport, MembershipImport) redefine it, and their POCO partials route
+            // IImport.ImportedMemberships(...) directly to ComputeRedefinedImportedMembershipsOperation
+            // on the matching subtype. This static extension on the abstract base is therefore
+            // unreachable at runtime and is documented as a deliberate NotSupportedException guard.
+            Assert.That(
+                () => ((IImport)null).ComputeImportedMembershipsOperation([]),
+                Throws.TypeOf<NotSupportedException>());
+
+            Assert.That(
+                () => new NamespaceImport().ComputeImportedMembershipsOperation([]),
+                Throws.TypeOf<NotSupportedException>());
+
+            Assert.That(
+                () => new MembershipImport().ComputeImportedMembershipsOperation([]),
+                Throws.TypeOf<NotSupportedException>());
         }
     }
 }
diff --git a/SysML2.NET/Extend/ImportExtensions.cs b/SysML2.NET/Extend/ImportExtensions.cs
index c75a1829..40a3de45 100644
--- a/SysML2.NET/Extend/ImportExtensions.cs
+++ b/SysML2.NET/Extend/ImportExtensions.cs
@@ -36,16 +36,33 @@ internal static class ImportExtensions
         /// <summary>
         /// Computes the derived property.
         /// </summary>
+        /// <remarks>
+        /// Spec-text-only: the UML <c>Import.importedElement</c> attribute has no OCL body of its
+        /// own. Each concrete subclass defines its own derivation rule
+        /// (<c>deriveMembershipImportImportedElement</c>: <c>importedElement = importedMembership.memberElement</c>,
+        /// and <c>deriveNamespaceImportImportedElement</c>: <c>importedElement = importedNamespace</c>).
+        /// Both subtype POCOs route their <c>importedElement</c> getter through this single static
+        /// extension, so the dispatch happens here via a switch on the subject's concrete type.
+        /// </remarks>
         /// <param name="importSubject">
         /// The subject <see cref="IImport"/>
         /// </param>
         /// <returns>
         /// the computed result
         /// </returns>
-        [System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
         internal static IElement ComputeImportedElement(this IImport importSubject)
         {
-            throw new NotSupportedException("Create a GitHub issue when this method is required");
+            if (importSubject == null)
+            {
+                throw new ArgumentNullException(nameof(importSubject));
+            }
+
+            return importSubject switch
+            {
+                IMembershipImport membershipImport => membershipImport.ImportedMembership?.MemberElement,
+                INamespaceImport namespaceImport => namespaceImport.ImportedNamespace,
+                _ => null
+            };
         }
 
         /// <summary>
@@ -76,15 +93,22 @@ internal static INamespace ComputeImportOwningNamespace(this IImport importSubje
         /// The expected collection of <see cref="IMembership" />
         /// </returns>
         /// <remarks>
-        /// This method is no longer called at runtime. The POCO classes (<see cref="NamespaceImport"/>,
-        /// <see cref="MembershipImport"/>) now provide explicit interface implementations of
-        /// <see cref="IImport.ImportedMemberships"/> that dispatch directly to their respective
-        /// <c>ComputeRedefinedImportedMembershipsOperation</c> extension methods.
+        /// The UML <c>Import.importedMemberships</c> operation is abstract (no body in the XMI). Both
+        /// concrete subclasses, <see cref="NamespaceImport"/> and <see cref="MembershipImport"/>, redefine
+        /// it with their own OCL <c>bodyCondition</c>s, and their POCO partials provide explicit-interface
+        /// implementations of <see cref="IImport.ImportedMemberships"/> that dispatch directly to their
+        /// respective <c>ComputeRedefinedImportedMembershipsOperation</c> extension methods. Consequently,
+        /// this static extension on the abstract base is never reached at runtime, and a deliberate
+        /// <see cref="NotSupportedException"/> guards any future direct call.
         /// </remarks>
         [System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
         internal static List<IMembership> ComputeImportedMembershipsOperation(this IImport importSubject, List<INamespace> excluded)
         {
-            throw new NotSupportedException("This method should not be called. Import subtypes handle dispatch via explicit interface implementations.");
+            throw new NotSupportedException(
+                "Import is abstract and its importedMemberships operation is redefined by every concrete subclass " +
+                "(NamespaceImport, MembershipImport). The POCO partials route IImport.ImportedMemberships(...) " +
+                "directly to ComputeRedefinedImportedMembershipsOperation on the matching subtype, so this static " +
+                "extension is unreachable at runtime.");
         }
     }
 }