test: retry E2E first navigation on ERR_NETWORK_CHANGED

tests/DrawTogether.End2End.Tests/DrawingMouseInteractionTests.cs

@@ -49,8 +49,10 @@ public async Task CanDrawWithMouse()
 
         _output.WriteLine($"Navigating to {endpoint}");
 
-        // Navigate to the app
-        await page.GotoAsync(endpoint.ToString());
+        // Navigate to the app. Retry on ERR_NETWORK_CHANGED: a freshly launched
+        // Chromium can abort its first navigation when Aspire's container network
+        // is still settling.
+        await GotoWithNetworkChangeRetryAsync(page, endpoint.ToString(), output: _output);
 
         // Handle authentication if needed - example for form-based auth
         await HandleNewUserRegistration(page, endpoint, _output);

tests/DrawTogether.End2End.Tests/DrawingTouchInteractionTests.cs

@@ -1,4 +1,4 @@
-using DrawTogether.End2End.Tests.Util;
+using DrawTogether.End2End.Tests.Util;
 using Microsoft.Playwright;
 using Xunit.Abstractions;
 using static DrawTogether.End2End.Tests.Util.DrawTogetherPlaywrightHelpers;
@@ -63,8 +63,10 @@ public async Task CanDrawWithTouch(int viewPortX, int viewPortY)
 
         _output.WriteLine($"Navigating to {endpoint}");
 
-        // Navigate to the app
-        await page.GotoAsync(endpoint.ToString());
+        // Navigate to the app. Retry on ERR_NETWORK_CHANGED: a freshly launched
+        // Chromium can abort its first navigation when Aspire's container network
+        // is still settling.
+        await GotoWithNetworkChangeRetryAsync(page, endpoint.ToString(), output: _output);
 
         // Handle authentication if needed - example for form-based auth
         await HandleNewUserRegistration(page, endpoint, _output);

tests/DrawTogether.End2End.Tests/Util/DrawTogetherPlaywrightHelpers.cs

@@ -5,6 +5,42 @@ namespace DrawTogether.End2End.Tests.Util;
 
 public static class DrawTogetherPlaywrightHelpers
 {
+    /// <summary>
+    /// The first navigation from a freshly launched Chromium can be aborted with
+    /// <c>net::ERR_NETWORK_CHANGED</c>: the browser tears down in-flight requests when it
+    /// observes a host network-state change, and Docker creating/removing container bridge
+    /// interfaces while Aspire starts resources produces exactly that.
+    /// See https://github.com/microsoft/playwright/issues/13062 (same signature, retry clears it)
+    /// and https://github.com/Grizzly-Endeavors/residuum/issues/592 (Docker bridge churn).
+    /// The abort happens before the page renders anything, so retrying is side-effect free.
+    /// </summary>
+    private const string NetworkChangedError = "ERR_NETWORK_CHANGED";
+
+    public static async Task<IResponse?> GotoWithNetworkChangeRetryAsync(
+        IPage page,
+        string url,
+        PageGotoOptions? options = null,
+        ITestOutputHelper? output = null,
+        int maxAttempts = 3)
+    {
+        for (var attempt = 1; ; attempt++)
+        {
+            try
+            {
+                return await page.GotoAsync(url, options);
+            }
+            catch (PlaywrightException ex) when (
+                attempt < maxAttempts &&
+                ex.Message.Contains(NetworkChangedError, StringComparison.Ordinal))
+            {
+                output?.WriteLine(
+                    $"Navigation to {url} aborted by {NetworkChangedError} " +
+                    $"(attempt {attempt}/{maxAttempts}); retrying.");
+                await Task.Delay(TimeSpan.FromMilliseconds(250 * attempt));
+            }
+        }
+    }
+
     public static async Task<ElementHandleBoundingBoxResult> LocateDrawingBox(IPage page, ITestOutputHelper output)
     {
         // Wait for the canvas to be present