diff --git a/src/Avalonia.Controls/AppBuilderBase.cs b/src/Avalonia.Controls/AppBuilderBase.cs
index 1610d33f9b..7af3deef34 100644
--- a/src/Avalonia.Controls/AppBuilderBase.cs
+++ b/src/Avalonia.Controls/AppBuilderBase.cs
@@ -14,6 +14,8 @@ namespace Avalonia.Controls
     /// <typeparam name="TAppBuilder">The type of the AppBuilder class itself.</typeparam>
     public abstract class AppBuilderBase<TAppBuilder> where TAppBuilder : AppBuilderBase<TAppBuilder>, new()
     {
+        private static bool s_setupWasAlreadyCalled;
+        
         /// <summary>
         /// Gets or sets the <see cref="IRuntimePlatform"/> instance.
         /// </summary>
@@ -207,6 +209,17 @@ namespace Avalonia.Controls
 
         public TAppBuilder UseAvaloniaModules() => AfterSetup(builder => SetupAvaloniaModules());
 
+        private bool CheckSetup { get; set; } = true;
+
+        /// <summary>
+        /// Set this AppBuilder to ignore the setup check. Used for testing purposes.
+        /// </summary>
+        internal TAppBuilder IgnoreSetupCheck()
+        {
+            CheckSetup = false;
+            return Self;
+        }
+
         private void SetupAvaloniaModules()
         {
             var moduleInitializers = from assembly in AvaloniaLocator.Current.GetService<IRuntimePlatform>().GetLoadedAssemblies()
@@ -252,6 +265,13 @@ namespace Avalonia.Controls
                 throw new InvalidOperationException("No rendering system configured.");
             }
 
+            if (s_setupWasAlreadyCalled && CheckSetup)
+            {
+                throw new InvalidOperationException("Setup was already called on one of AppBuilder instances");
+            }
+
+            s_setupWasAlreadyCalled = true;
+
             Instance.RegisterServices();
             RuntimePlatformServicesInitializer();
             WindowingSubsystemInitializer();
diff --git a/src/Avalonia.Controls/Application.cs b/src/Avalonia.Controls/Application.cs
index abae080515..06c1a8b4cc 100644
--- a/src/Avalonia.Controls/Application.cs
+++ b/src/Avalonia.Controls/Application.cs
@@ -175,6 +175,15 @@ namespace Avalonia
             closable.Closed += (s, e) => source.Cancel();
             Dispatcher.UIThread.MainLoop(source.Token);
         }
+        
+        /// <summary>
+        /// Runs the application's main loop until the <see cref="CancellationToken"/> is cancelled.
+        /// </summary>
+        /// <param name="token">The token to track</param>
+        public void Run(CancellationToken token)
+        {
+            Dispatcher.UIThread.MainLoop(token);
+        }
 
         /// <summary>
         /// Exits the application
diff --git a/tests/Avalonia.Controls.UnitTests/AppBuilderTests.cs b/tests/Avalonia.Controls.UnitTests/AppBuilderTests.cs
index 867f740a3a..60c53d126c 100644
--- a/tests/Avalonia.Controls.UnitTests/AppBuilderTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/AppBuilderTests.cs
@@ -65,6 +65,7 @@ namespace Avalonia.Controls.UnitTests
             {
                 ResetModuleLoadStates();
                 AppBuilder.Configure<App>()
+                    .IgnoreSetupCheck()
                     .UseWindowingSubsystem(() => { })
                     .UseRenderingSubsystem(() => { })
                     .UseAvaloniaModules()
@@ -81,6 +82,7 @@ namespace Avalonia.Controls.UnitTests
             {
                 ResetModuleLoadStates();
                 var builder = AppBuilder.Configure<App>()
+                    .IgnoreSetupCheck()
                     .UseWindowingSubsystem(() => { })
                     .UseRenderingSubsystem(() => { }, "Direct2D1");
                 builder.UseAvaloniaModules().SetupWithoutStarting();
@@ -90,6 +92,7 @@ namespace Avalonia.Controls.UnitTests
 
                 ResetModuleLoadStates();
                 builder = AppBuilder.Configure<App>()
+                    .IgnoreSetupCheck()
                     .UseWindowingSubsystem(() => { })
                     .UseRenderingSubsystem(() => { }, "Skia");
                 builder.UseAvaloniaModules().SetupWithoutStarting();
@@ -99,13 +102,14 @@ namespace Avalonia.Controls.UnitTests
             }
         }
 
-        [Fact (Skip = "We don't have rendering modules with dependencies right now")]
+        [Fact]
         public void LoadsRenderingModuleWithoutDependenciesWhenNoModuleMatches()
         {
             using (AvaloniaLocator.EnterScope())
             {
                 ResetModuleLoadStates();
                 var builder = AppBuilder.Configure<App>()
+                    .IgnoreSetupCheck()
                     .UseWindowingSubsystem(() => { })
                     .UseRenderingSubsystem(() => { }, "TBD");
                 builder.UseAvaloniaModules().SetupWithoutStarting();