diff --git a/src/Headless/Avalonia.Headless/HeadlessUnitTestSession.cs b/src/Headless/Avalonia.Headless/HeadlessUnitTestSession.cs index a3059c6d3e..12f8515209 100644 --- a/src/Headless/Avalonia.Headless/HeadlessUnitTestSession.cs +++ b/src/Headless/Avalonia.Headless/HeadlessUnitTestSession.cs @@ -89,6 +89,11 @@ public sealed class HeadlessUnitTestSession : IDisposable appBuilder.SetupWithoutStarting(); + if (!Dispatcher.UIThread.SupportsRunLoops) + { + throw new InvalidOperationException("Avalonia Headless platform has failed to initialize."); + } + // ReSharper disable once AccessToModifiedClosure tcs.SetResult(new HeadlessUnitTestSession(entryPointType, Application.Current!, SynchronizationContext.Current!, Dispatcher.UIThread, cancellationTokenSource));