Fix #224: Containment pattern optimized to support reference

CLAUDE.md

@@ -29,6 +29,8 @@ dotnet-coverage collect "dotnet test SysML2.NET.sln --no-build" -f xml -o covera
 
 Test framework: **NUnit**. Test classes use `[TestFixture]` and `[Test]` attributes.
 
+**When writing or modifying unit tests** in any `*.Tests/` project: read `TESTING.md` at the repo root for the NUnit conventions (one `[Test]` per method-under-test, `Assert.That` everywhere, `Assert.EnterMultipleScope` only for consecutive asserts, mandatory positive + negative coverage, assertion idiom preferences, `Verify{MethodUnderTest}` naming).
+
 ## Architecture
 
 ### Code Generation
@@ -155,3 +157,4 @@ Auto-generated DTOs use structured namespaces reflecting the KerML/SysML package
 - Use meaningful variable names instead of single-letter names in any context (e.g., 'charIndex' instead of 'i', 'currentChar' instead of 'c', 'element' instead of 'e')
 - Use 'NotSupportedException' (not 'NotImplementedException') for placeholder/stub methods that require manual implementation
 - Prefer C# property patterns ('x is IType { Prop: value }') over declared-variable-plus-predicate form ('x is IType name && name.Prop == value') when the narrowed variable is only consulted once; the property-pattern form is more concise and intent-revealing
+- Surround every braced block (`if`, `else if`, `while`, `for`, `foreach`, `switch`, `using`, `try`/`catch`/`finally`, `lock`, `do…while`, anonymous `{ }`) with a blank line on both sides — the rule does NOT apply at the very start/end of a method body, nor between a `}` and a continuation keyword (`else`, `catch`, `finally`, `while` of `do…while`) that belongs to the same control flow

SysML2.NET.CodeGenerator.Tests/Generators/UmlHandleBarsGenerators/UmlCorePocoValidationGeneratorTestFixture.cs

@@ -0,0 +1,69 @@
+// -------------------------------------------------------------------------------------------------
+// <copyright file="UmlCorePocoValidationGeneratorTestFixture.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.CodeGenerator.Tests.Generators.UmlHandleBarsGenerators
+{
+    using System.IO;
+    using System.Threading.Tasks;
+
+    using NUnit.Framework;
+
+    using SysML2.NET.CodeGenerator.Generators.UmlHandleBarsGenerators;
+
+    [TestFixture]
+    public class UmlCorePocoValidationGeneratorTestFixture
+    {
+        private DirectoryInfo outputDirectory;
+        private UmlCorePocoValidationGenerator generator;
+
+        [OneTimeSetUp]
+        public void OneTimeSetup()
+        {
+            var directoryInfo = new DirectoryInfo(TestContext.CurrentContext.TestDirectory);
+
+            var path = Path.Combine("UML", "_SysML2.NET.AutoGenExtensions.ElementExtensions");
+
+            this.outputDirectory = directoryInfo.CreateSubdirectory(path);
+            this.generator = new UmlCorePocoValidationGenerator();
+        }
+
+        [Test]
+        public async Task VerifyElementExtensionsAreGenerated()
+        {
+            await Assert.ThatAsync(
+                () => this.generator.GenerateAsync(GeneratorSetupFixture.XmiReaderResult, this.outputDirectory),
+                Throws.Nothing);
+        }
+
+        [Test]
+        [Category("Expected")]
+        public async Task VerifyExpectedElementExtensionsMatches()
+        {
+            var generatedCode = await this.generator.GenerateElementExtensions(
+                GeneratorSetupFixture.XmiReaderResult,
+                this.outputDirectory);
+
+            var expected = await File.ReadAllTextAsync(Path.Combine(TestContext.CurrentContext.TestDirectory,
+                "Expected/UML/Core/AutoGenExtensions/ElementExtensions.cs"));
+
+            Assert.That(generatedCode, Is.EqualTo(expected));
+        }
+    }
+}

SysML2.NET.CodeGenerator.Tests/SysML2.NET.CodeGenerator.Tests.csproj

@@ -19,7 +19,11 @@
     <Compile Remove="Extensions\**" />
     <EmbeddedResource Remove="Extensions\**" />
     <None Remove="Extensions\**" />
+    <Compile Remove="Expected\UML\Core\AutoGenExtensions\ElementExtensions.cs" />
     <Compile Remove="Expected\UML\Core\AutoGenReaders\AnnotatingElementReader.cs" />
+    <None Include="Expected\UML\Core\AutoGenExtensions\ElementExtensions.cs">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </None>
     <None Include="Expected\UML\Core\AutoGenReaders\AnnotatingElementReader.cs">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </None>