From fc4e457bfa161ac6c3920ec056c98552bb53227d Mon Sep 17 00:00:00 2001
From: Tom Longhurst <30480171+thomhurst@users.noreply.github.com>
Date: Sat, 29 Nov 2025 19:50:23 +0000
Subject: [PATCH 1/2] fix: ensure IClassConstructor and ITestEndEventReceiver
 share the same instance for state management

---
 TUnit.Core/Helpers/ClassConstructorHelper.cs |  6 +--
 TUnit.TestProject/Bugs/3939/Tests.cs         | 53 ++++++++++++++++++++
 2 files changed, 56 insertions(+), 3 deletions(-)
 create mode 100644 TUnit.TestProject/Bugs/3939/Tests.cs

diff --git a/TUnit.Core/Helpers/ClassConstructorHelper.cs b/TUnit.Core/Helpers/ClassConstructorHelper.cs
index 136a6132b1..8430cfb63b 100644
--- a/TUnit.Core/Helpers/ClassConstructorHelper.cs
+++ b/TUnit.Core/Helpers/ClassConstructorHelper.cs
@@ -50,9 +50,9 @@ public static class ClassConstructorHelper
             return null;
         }
 
-        // Use the ClassConstructor to create the instance
-        var classConstructorType = classConstructorAttribute.ClassConstructorType;
-        var classConstructor = (IClassConstructor)Activator.CreateInstance(classConstructorType)!;
+        // Reuse existing ClassConstructor if already set, otherwise create new instance
+        var classConstructor = testBuilderContext.ClassConstructor
+            ?? (IClassConstructor)Activator.CreateInstance(classConstructorAttribute.ClassConstructorType)!;
 
         testBuilderContext.ClassConstructor = classConstructor;
 
diff --git a/TUnit.TestProject/Bugs/3939/Tests.cs b/TUnit.TestProject/Bugs/3939/Tests.cs
new file mode 100644
index 0000000000..215a5be18c
--- /dev/null
+++ b/TUnit.TestProject/Bugs/3939/Tests.cs
@@ -0,0 +1,53 @@
+using System.Diagnostics.CodeAnalysis;
+using TUnit.Core.Interfaces;
+using TUnit.TestProject.Attributes;
+
+namespace TUnit.TestProject.Bugs._3939;
+
+/// <summary>
+/// Regression test for issue #3939: IClassConstructor and ITestEndEventReceiver
+/// should use the same instance so that state can be shared (e.g., DI scope disposal).
+/// </summary>
+public sealed class ScopedClassConstructor : IClassConstructor, ITestEndEventReceiver
+{
+    private object? _scope;
+
+    public Task<object> Create([DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicConstructors)] Type type, ClassConstructorMetadata classConstructorMetadata)
+    {
+        // Simulate creating a DI scope - this should be available in OnTestEnd
+        _scope = new object();
+        return Task.FromResult<object>(new Tests());
+    }
+
+    public ValueTask OnTestEnd(TestContext context)
+    {
+        // This should be called on the SAME instance that Create() was called on
+        // If _scope is null, it means a different instance was used - this is the bug!
+        if (_scope == null)
+        {
+            throw new InvalidOperationException(
+                "Issue #3939: _scope was null in OnTestEnd(), indicating a different IClassConstructor " +
+                "instance was used than the one where Create() was called. " +
+                "IClassConstructor and ITestEndEventReceiver must use the same instance.");
+        }
+
+        // Simulate disposing the scope
+        _scope = null;
+        return default;
+    }
+
+    public int Order => 0;
+}
+
+[EngineTest(ExpectedResult.Pass)]
+[ClassConstructor<ScopedClassConstructor>]
+public sealed class Tests
+{
+    [Test]
+    public Task TestMethod()
+    {
+        // The actual test - just verifies the test runs
+        // The real assertion is in OnTestEnd - it will throw if different instances are used
+        return Task.CompletedTask;
+    }
+}

From 8fdecf76c8e0f167f68f0d2f4763819d96402038 Mon Sep 17 00:00:00 2001
From: Tom Longhurst <30480171+thomhurst@users.noreply.github.com>
Date: Sat, 29 Nov 2025 20:49:09 +0000
Subject: [PATCH 2/2] fix: ensure IClassConstructor and ITestEndEventReceiver
 share the same instance to maintain state

---
 TUnit.Core/TestBuilderContext.cs     | 6 +++++-
 TUnit.Engine/Building/TestBuilder.cs | 3 ++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/TUnit.Core/TestBuilderContext.cs b/TUnit.Core/TestBuilderContext.cs
index cac0481205..25b20c65d4 100644
--- a/TUnit.Core/TestBuilderContext.cs
+++ b/TUnit.Core/TestBuilderContext.cs
@@ -57,7 +57,11 @@ internal static TestBuilderContext FromTestContext(TestContext testContext, IDat
     {
         return new TestBuilderContext
         {
-            Events = testContext.InternalEvents, TestMetadata = testContext.Metadata.TestDetails.MethodMetadata, DataSourceAttribute = dataSourceAttribute, StateBag = testContext.StateBag.Items,
+            Events = testContext.InternalEvents,
+            TestMetadata = testContext.Metadata.TestDetails.MethodMetadata,
+            DataSourceAttribute = dataSourceAttribute,
+            StateBag = testContext.StateBag.Items,
+            ClassConstructor = testContext.ClassConstructor,
         };
     }
 }
diff --git a/TUnit.Engine/Building/TestBuilder.cs b/TUnit.Engine/Building/TestBuilder.cs
index a854f4e2df..cc6da989b9 100644
--- a/TUnit.Engine/Building/TestBuilder.cs
+++ b/TUnit.Engine/Building/TestBuilder.cs
@@ -290,7 +290,8 @@ public async Task<IEnumerable<AbstractExecutableTest>> BuildTestsFromMetadataAsy
                                     Events = new TestContextEvents(),
                                     StateBag = new ConcurrentDictionary<string, object?>(),
                                     DataSourceAttribute = methodDataSource,
-                                    InitializedAttributes = testBuilderContext.InitializedAttributes  // Preserve attributes from parent context
+                                    InitializedAttributes = testBuilderContext.InitializedAttributes,  // Preserve attributes from parent context
+                                    ClassConstructor = testBuilderContext.ClassConstructor  // Preserve ClassConstructor for instance creation
                                 };
 
                                 classData = DataUnwrapper.Unwrap(await classDataFactory() ?? []);