Fix flaky headless navigation tests

tests/Avalonia.Controls.WebView.Tests/HeadlessAdapterTests.cs

@@ -67,7 +67,7 @@ public async Task NativeWebView_Navigation_And_Events()
 
         var uri = new Uri("https://example.com");
         webView.Source = uri;
-        await DoDelay();
+        await WaitFor(() => navCompleted);
 
         Assert.True(navStarted);
         Assert.True(navCompleted);
@@ -89,14 +89,14 @@ public async Task NativeWebView_NavigateToString_And_Refresh()
         window.Show();
 
         webView.NavigateToString("<html>test</html>");
-        await DoDelay();
+        await WaitFor(() => navCompleted);
 
         Assert.True(navCompleted);
         Assert.Equal(WebViewHelper.EmptyPage, webView.Source);
 
         navCompleted = false;
         Assert.True(webView.Refresh());
-        await DoDelay();
+        await WaitFor(() => navCompleted);
         Assert.True(navCompleted);
     }
 
@@ -390,7 +390,7 @@ private async Task ReattachAsync(Panel panel, NativeWebView webView)
         await DoDelay();
     }
 
-    [AvaloniaFact(Skip = "Flaky test")]
+    [AvaloniaFact]
     public async Task NativeWebView_NavigateToString_With_BaseUri()
     {
         var window = new Window();
@@ -403,7 +403,7 @@ public async Task NativeWebView_NavigateToString_With_BaseUri()
 
         var baseUri = new Uri("https://example.com/");
         webView.NavigateToString("<html>test</html>", baseUri);
-        await DoDelay();
+        await WaitFor(() => navCompleted);
 
         Assert.True(navCompleted);
         Assert.Equal(baseUri, webView.Source);

tests/Avalonia.Controls.WebView.Tests/HeadlessTestsBase.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics;
 using System.Threading.Tasks;
 using Avalonia.Threading;
 
@@ -18,6 +19,23 @@ public async Task DoDelay()
         Dispatcher.UIThread.RunJobs();
     }
 
+    /// <summary>
+    /// Pumps the dispatcher until <paramref name="condition"/> is true or the timeout runs out.
+    /// The headless adapter completes navigation on the thread pool and reports it back through the dispatcher,
+    /// so a fixed delay is not enough on a busy machine. On timeout this returns and the caller's assert fails.
+    /// </summary>
+    public async Task WaitFor(Func<bool> condition, int timeoutMs = 5000)
+    {
+        var stopwatch = Stopwatch.StartNew();
+        while (true)
+        {
+            Dispatcher.UIThread.RunJobs();
+            if (condition() || stopwatch.ElapsedMilliseconds > timeoutMs)
+                return;
+            await Task.Delay(5);
+        }
+    }
+
     protected Task WaitForAdapterCreation(NativeWebView webView)
     {
         var tcs = new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);

tests/Avalonia.Controls.WebView.Tests/NativeWebViewTests.cs

@@ -86,7 +86,7 @@ public async Task Should_Navigate_If_Navigate_Called_Before_Window_Show()
         webView.Navigate(uri); // before adding to window
         window.Content = webView;
         window.Show();
-        await DoDelay();
+        await WaitFor(() => navCompleted);
 
         Assert.Equal(uri, webView.Source);
         Assert.True(navCompleted);
@@ -107,7 +107,7 @@ public async Task Should_NavigateToString_If_Called_Before_Window_Show()
         webView.NavigateToString("<html>abc</html>"); // before adding to window
         window.Content = webView;
         window.Show();
-        await DoDelay();
+        await WaitFor(() => navCompleted);
 
         Assert.Equal(WebViewHelper.EmptyPage, webView.Source);
         Assert.True(navCompleted);