diff --git a/nukebuild/Build.cs b/nukebuild/Build.cs
index 9fcb9d6b7f..f0f677b844 100644
--- a/nukebuild/Build.cs
+++ b/nukebuild/Build.cs
@@ -221,6 +221,7 @@ partial class Build : NukeBuild
             RunCoreTest("Avalonia.Markup.Xaml.UnitTests");
             RunCoreTest("Avalonia.Skia.UnitTests");
             RunCoreTest("Avalonia.ReactiveUI.UnitTests");
+            RunCoreTest("Avalonia.PlatformSupport.UnitTests");
         });
 
     Target RunRenderTests => _ => _
diff --git a/src/Avalonia.PlatformSupport/AssetLoader.cs b/src/Avalonia.PlatformSupport/AssetLoader.cs
index fb03ec2f6e..0e33c3d4c7 100644
--- a/src/Avalonia.PlatformSupport/AssetLoader.cs
+++ b/src/Avalonia.PlatformSupport/AssetLoader.cs
@@ -14,14 +14,14 @@ namespace Avalonia.PlatformSupport
     /// </summary>
     public class AssetLoader : IAssetLoader
     {
-        private static AssemblyDescriptorResolver s_assemblyDescriptorResolver = new();
+        private static IAssemblyDescriptorResolver s_assemblyDescriptorResolver = new AssemblyDescriptorResolver();
 
         private AssemblyDescriptor? _defaultResmAssembly;
 
         /// <remarks>
         /// Introduced for tests.
         /// </remarks>
-        internal static void SetAssemblyDescriptorResolver(AssemblyDescriptorResolver resolver) =>
+        internal static void SetAssemblyDescriptorResolver(IAssemblyDescriptorResolver resolver) =>
             s_assemblyDescriptorResolver = resolver;
 
         /// <summary>
@@ -182,13 +182,13 @@ namespace Avalonia.PlatformSupport
             throw new ArgumentException($"Unsupported url type: " + uri.Scheme, nameof(uri));
         }
 
-        private (AssemblyDescriptor asm, string path) GetResAsmAndPath(Uri uri)
+        private (IAssemblyDescriptor asm, string path) GetResAsmAndPath(Uri uri)
         {
             var asm = s_assemblyDescriptorResolver.GetAssembly(uri.Authority);
             return (asm, uri.GetUnescapeAbsolutePath());
         }
         
-        private AssemblyDescriptor? GetAssembly(Uri? uri)
+        private IAssemblyDescriptor? GetAssembly(Uri? uri)
         {
             if (uri != null)
             {
diff --git a/src/Avalonia.PlatformSupport/Avalonia.PlatformSupport.csproj b/src/Avalonia.PlatformSupport/Avalonia.PlatformSupport.csproj
index 420ac0796c..5336f1e630 100644
--- a/src/Avalonia.PlatformSupport/Avalonia.PlatformSupport.csproj
+++ b/src/Avalonia.PlatformSupport/Avalonia.PlatformSupport.csproj
@@ -19,6 +19,6 @@
 
   <ItemGroup>
     <InternalsVisibleTo Include="$(AssemblyName).UnitTests, PublicKey=0024000004800000940000000602000000240000525341310004000001000100c1bba1142285fe0419326fb25866ba62c47e6c2b5c1ab0c95b46413fad375471232cb81706932e1cef38781b9ebd39d5100401bacb651c6c5bbf59e571e81b3bc08d2a622004e08b1a6ece82a7e0b9857525c86d2b95fab4bc3dce148558d7f3ae61aa3a234086902aeface87d9dfdd32b9d2fe3c6dd4055b5ab4b104998bd87" />
-    <InternalsVisibleTo Include="DynamicProxyGenAssembly2, PublicKey=0024000004800000940000000602000000240000525341310004000001000100c1bba1142285fe0419326fb25866ba62c47e6c2b5c1ab0c95b46413fad375471232cb81706932e1cef38781b9ebd39d5100401bacb651c6c5bbf59e571e81b3bc08d2a622004e08b1a6ece82a7e0b9857525c86d2b95fab4bc3dce148558d7f3ae61aa3a234086902aeface87d9dfdd32b9d2fe3c6dd4055b5ab4b104998bd87" />
+    <InternalsVisibleTo Include="DynamicProxyGenAssembly2, PublicKey=0024000004800000940000000602000000240000525341310004000001000100c547cac37abd99c8db225ef2f6c8a3602f3b3606cc9891605d02baa56104f4cfc0734aa39b93bf7852f7d9266654753cc297e7d2edfe0bac1cdcf9f717241550e0a7b191195b7667bb4f64bcb8e2121380fd1d9d46ad2d92d2d15605093924cceaf74c4861eff62abf69b9291ed0a340e113be11e6a7d3113e92484cf7045cc7" />
   </ItemGroup>
 </Project>
diff --git a/src/Avalonia.PlatformSupport/Internal/AssemblyDescriptor.cs b/src/Avalonia.PlatformSupport/Internal/AssemblyDescriptor.cs
index a3de7f2b8a..64ffec8482 100644
--- a/src/Avalonia.PlatformSupport/Internal/AssemblyDescriptor.cs
+++ b/src/Avalonia.PlatformSupport/Internal/AssemblyDescriptor.cs
@@ -6,7 +6,15 @@ using Avalonia.Utilities;
 
 namespace Avalonia.PlatformSupport.Internal;
 
-internal class AssemblyDescriptor
+internal interface IAssemblyDescriptor
+{
+    Assembly Assembly { get; }
+    Dictionary<string, IAssetDescriptor>? Resources { get; }
+    Dictionary<string, IAssetDescriptor>? AvaloniaResources { get; }
+    string? Name { get; }
+}
+
+internal class AssemblyDescriptor : IAssemblyDescriptor
 {
     public AssemblyDescriptor(Assembly assembly)
     {
diff --git a/src/Avalonia.PlatformSupport/Internal/AssemblyDescriptorResolver.cs b/src/Avalonia.PlatformSupport/Internal/AssemblyDescriptorResolver.cs
index a78051a9c4..28ae35d57d 100644
--- a/src/Avalonia.PlatformSupport/Internal/AssemblyDescriptorResolver.cs
+++ b/src/Avalonia.PlatformSupport/Internal/AssemblyDescriptorResolver.cs
@@ -5,11 +5,16 @@ using System.Reflection;
 
 namespace Avalonia.PlatformSupport.Internal;
 
-internal class AssemblyDescriptorResolver
+internal interface IAssemblyDescriptorResolver
 {
-    private readonly Dictionary<string, AssemblyDescriptor> _assemblyNameCache = new();
+    IAssemblyDescriptor GetAssembly(string name);
+}
+
+internal class AssemblyDescriptorResolver: IAssemblyDescriptorResolver
+{
+    private readonly Dictionary<string, IAssemblyDescriptor> _assemblyNameCache = new();
 
-    public AssemblyDescriptor GetAssembly(string name)
+    public IAssemblyDescriptor GetAssembly(string name)
     {
         if (name == null)
             throw new ArgumentNullException(nameof(name));
diff --git a/tests/Avalonia.PlatformSupport.UnitTests/AssetLoaderTests.cs b/tests/Avalonia.PlatformSupport.UnitTests/AssetLoaderTests.cs
index f950fb7e99..dfd195073b 100644
--- a/tests/Avalonia.PlatformSupport.UnitTests/AssetLoaderTests.cs
+++ b/tests/Avalonia.PlatformSupport.UnitTests/AssetLoaderTests.cs
@@ -16,7 +16,7 @@ public class AssetLoaderTests
 
     static AssetLoaderTests()
     {
-        var resolver = Mock.Of<AssemblyDescriptorResolver>();
+        var resolver = Mock.Of<IAssemblyDescriptorResolver>();
 
         var descriptor = CreateAssemblyDescriptor(AssemblyNameWithWhitespace);
         Mock.Get(resolver).Setup(x => x.GetAssembly(AssemblyNameWithWhitespace)).Returns(descriptor);
@@ -49,13 +49,13 @@ public class AssetLoaderTests
         Assert.Equal(AssemblyNameWithNonAscii, assemblyActual?.FullName);
     }
 
-    private static AssemblyDescriptor CreateAssemblyDescriptor(string assemblyName)
+    private static IAssemblyDescriptor CreateAssemblyDescriptor(string assemblyName)
     {
         var assembly = Mock.Of<MockAssembly>();
         Mock.Get(assembly).Setup(x => x.GetName()).Returns(new AssemblyName(assemblyName));
         Mock.Get(assembly).Setup(x => x.FullName).Returns(assemblyName);
 
-        var descriptor = Mock.Of<AssemblyDescriptor>();
+        var descriptor = Mock.Of<IAssemblyDescriptor>();
         Mock.Get(descriptor).Setup(x => x.Assembly).Returns(assembly);
         return descriptor;
     }