diff --git a/tests/ClaudeDo.Installer.Tests/ClaudeDo.Installer.Tests.csproj b/tests/ClaudeDo.Installer.Tests/ClaudeDo.Installer.Tests.csproj
index 5db6af4..3aef282 100644
--- a/tests/ClaudeDo.Installer.Tests/ClaudeDo.Installer.Tests.csproj
+++ b/tests/ClaudeDo.Installer.Tests/ClaudeDo.Installer.Tests.csproj
@@ -2,8 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net8.0-windows</TargetFramework>
-    <UseWPF>true</UseWPF>
-    <ImplicitUsings>enable</ImplicitUsings>
+<ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
 
     <IsPackable>false</IsPackable>
diff --git a/tests/ClaudeDo.Installer.Tests/FakeHttpMessageHandler.cs b/tests/ClaudeDo.Installer.Tests/FakeHttpMessageHandler.cs
index 00f009c..960a8fb 100644
--- a/tests/ClaudeDo.Installer.Tests/FakeHttpMessageHandler.cs
+++ b/tests/ClaudeDo.Installer.Tests/FakeHttpMessageHandler.cs
@@ -6,6 +6,8 @@ namespace ClaudeDo.Installer.Tests;
 internal sealed class FakeHttpMessageHandler : HttpMessageHandler
 {
     private readonly Func<HttpRequestMessage, HttpResponseMessage> _handler;
+    private readonly object _lock = new();
+    private readonly List<HttpRequestMessage> _requests = new();
 
     public FakeHttpMessageHandler(Func<HttpRequestMessage, HttpResponseMessage> handler)
     {
@@ -17,11 +19,14 @@ internal sealed class FakeHttpMessageHandler : HttpMessageHandler
     {
     }
 
-    public List<HttpRequestMessage> Requests { get; } = new();
+    public IReadOnlyList<HttpRequestMessage> Requests
+    {
+        get { lock (_lock) return _requests.ToArray(); }
+    }
 
     protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
     {
-        Requests.Add(request);
+        lock (_lock) _requests.Add(request);
         return Task.FromResult(_handler(request));
     }
 }