test case added

Author: devanathan-vaithiyanathan

src/Controls/tests/TestCases.HostApp/Issues/Issue37635.cs

@@ -0,0 +1,129 @@
+using System.Runtime.CompilerServices;
+using System.Windows.Input;
+
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 37635, "BackButtonBehavior.Command retains discarded behaviors", PlatformAffected.All)]
+public class Issue37635 : Shell
+{
+    public Issue37635()
+    {
+        Items.Add(new ShellContent
+        {
+            Title = "Issue 37635",
+            ContentTemplate = new DataTemplate(() => new Issue37635Page())
+        });
+    }
+}
+
+file class Issue37635Page : ContentPage
+{
+    const int CohortSize = 30;
+    readonly Issue37635Command _sharedCommand = new();
+    readonly Label _resultLabel;
+
+    public Issue37635Page()
+    {
+        Title = "BackButtonBehavior leak";
+
+        _resultLabel = new Label
+        {
+            AutomationId = "ResultLabel",
+            Text = "Run the test to check retained payloads."
+        };
+
+        var runButton = new Button
+        {
+            AutomationId = "RunTestButton",
+            Text = "Run test"
+        };
+        runButton.Clicked += OnRunTestClicked;
+
+        Content = new VerticalStackLayout
+        {
+            Padding = 24,
+            Spacing = 16,
+            Children =
+            {
+                new Label
+                {
+                    FontAttributes = FontAttributes.Bold,
+                    FontSize = 22,
+                    Text = "BackButtonBehavior.Command memory test"
+                },
+                new Label
+                {
+                    Text = "Creates discarded behaviors with 1 MB BindingContext payloads. The shared command must not retain them."
+                },
+                runButton,
+                _resultLabel
+            }
+        };
+    }
+
+    async void OnRunTestClicked(object sender, EventArgs e)
+    {
+        _resultLabel.Text = "Collecting...";
+
+        WeakReference[] control = CreateCohort(null);
+        WeakReference[] command = CreateCohort(_sharedCommand);
+
+        try
+        {
+            await GarbageCollectionHelper.WaitForGC(5000, control.Concat(command).ToArray());
+        }
+        catch
+        {
+            // Report retained references so the UI test fails with the observed counts.
+        }
+
+        int controlAlive = control.Count(reference => reference.IsAlive);
+        int commandAlive = command.Count(reference => reference.IsAlive);
+        _resultLabel.Text = $"Control: {controlAlive}/{CohortSize}; Command: {commandAlive}/{CohortSize}";
+        GC.KeepAlive(_sharedCommand);
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static WeakReference[] CreateCohort(ICommand command)
+    {
+        var references = new WeakReference[CohortSize];
+
+        for (int index = 0; index < CohortSize; index++)
+        {
+            references[index] = CreatePayloadReference(command);
+        }
+
+        return references;
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static WeakReference CreatePayloadReference(ICommand command)
+    {
+        var payload = new Issue37635Payload();
+        var behavior = new BackButtonBehavior
+        {
+            BindingContext = payload,
+            Command = command
+        };
+
+        return new WeakReference(payload);
+    }
+}
+
+file sealed class Issue37635Payload
+{
+    readonly byte[] _bytes = new byte[1024 * 1024];
+}
+
+file sealed class Issue37635Command : ICommand
+{
+    public event EventHandler CanExecuteChanged;
+
+    public bool CanExecute(object parameter) => true;
+
+    public void Execute(object parameter)
+    {
+    }
+
+    public void RaiseCanExecuteChanged() => CanExecuteChanged?.Invoke(this, EventArgs.Empty);
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue37635.cs

@@ -0,0 +1,27 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue37635 : _IssuesUITest
+{
+    const string ExpectedResult = "Control: 0/30; Command: 0/30";
+
+    public Issue37635(TestDevice device) : base(device)
+    {
+    }
+
+    public override string Issue => "BackButtonBehavior.Command retains discarded behaviors";
+
+    [Test]
+    [Category(UITestCategories.Shell)]
+    public void BackButtonBehaviorCommandDoesNotRetainDiscardedBehavior()
+    {
+        App.WaitForElement("RunTestButton");
+        App.Tap("RunTestButton");
+
+        bool collected = App.WaitForTextToBePresentInElement("ResultLabel", ExpectedResult);
+        Assert.That(collected, Is.True, "Expected the control and shared-command cohorts to be fully collected.");
+    }
+}