diff --git a/backend/tests/Squidex.Domain.Apps.Core.Tests/TestHelpers/JintHostContractVerification.cs b/backend/tests/Squidex.Domain.Apps.Core.Tests/TestHelpers/JintHostContractVerification.cs
new file mode 100644
index 000000000..3fe8ea3b0
--- /dev/null
+++ b/backend/tests/Squidex.Domain.Apps.Core.Tests/TestHelpers/JintHostContractVerification.cs
@@ -0,0 +1,35 @@
+// ==========================================================================
+//  Squidex Headless CMS
+// ==========================================================================
+//  Copyright (c) Squidex UG (haftungsbeschraenkt)
+//  All rights reserved. Licensed under the MIT license.
+// ==========================================================================
+
+using System.Runtime.CompilerServices;
+
+namespace Squidex.Domain.Apps.Core.TestHelpers;
+
+/// <summary>
+/// Turns on Jint's host-contract verifiers for this test assembly.
+/// </summary>
+/// <remarks>
+/// The scripting integration defines several Jint extension points - the ContentWrapper objects override
+/// GetOwnProperty and ProbeOwnProperty, and the engine trusts both without re-verifying them on the hot
+/// path. A hook that contradicts another therefore fails silently in production: a key vanishes from every
+/// enumeration, or a read resolves on the prototype for a property that exists. With the switch on, Jint
+/// recomputes the answer the fast paths exist to avoid and throws on the first disagreement, so these tests
+/// are the checker.
+/// <para>
+/// It has to be set before the first use of any Jint type - the flag is read once at type initialization -
+/// which is what the module initializer guarantees. Never turn it on in production: the verifiers
+/// deliberately redo the work they check.
+/// </para>
+/// </remarks>
+internal static class JintHostContractVerification
+{
+    [ModuleInitializer]
+    internal static void Enable()
+    {
+        AppContext.SetSwitch("Jint.EnableHostContractVerification", true);
+    }
+}