Enhance Prism.Maui navigation and test robustness

Improves `TabbedPage` selected tab resolution by matching registered view names alongside CLR type names, addressing scenarios where they diverge.

Refactors `PageNavigationService` unit tests for increased reliability:
- Converts `async void` tests to `async Task`.
- Explicitly asserts `INavigationResult` for navigation outcomes.
- Introduces a shared `PageNavigationEventRecorder` for consistent tracking of page lifecycle events across DI-resolved instances.
- Adds helper methods for navigating complex visual trees (e.g., finding tabbed or flyout pages).

Updates `EventToCommandBehavior` tests to use `CollectionView` and a more flexible mock for event raising, ensuring accurate behavior simulation.

Author: dansiegel

src/Maui/Prism.Maui/Navigation/PageNavigationService.cs

@@ -375,9 +375,23 @@ static TabbedPage GetTabbedPage(Element page) =>
             var parts = tabName.Split('|');
             Page selectedChild = null;
             if (parts.Length == 1)
-                selectedChild = tabbedPage.Children.FirstOrDefault(x => ViewModelLocator.GetNavigationName(x) == tabName || (x is NavigationPage navPage && ViewModelLocator.GetNavigationName(navPage.RootPage) == tabName));
+            {
+                var tabRegistration = Registry.Registrations.FirstOrDefault(x => x.Name == tabName);
+                selectedChild = tabbedPage.Children.FirstOrDefault(x =>
+                    ViewModelLocator.GetNavigationName(x) == tabName
+                    || (x is NavigationPage navPage && ViewModelLocator.GetNavigationName(navPage.RootPage) == tabName)
+                    || (tabRegistration is not null && x is NavigationPage np && IsPage(np.RootPage, tabRegistration, tabName))
+                    || (tabRegistration is not null && IsPage(x, tabRegistration, tabName)));
+            }
             else if (parts.Length == 2)
-                selectedChild = tabbedPage.Children.FirstOrDefault(x => x is NavigationPage navPage && ViewModelLocator.GetNavigationName(navPage) == parts[0] && ViewModelLocator.GetNavigationName(navPage.RootPage) == parts[1]);
+            {
+                var rootRegistration = Registry.Registrations.FirstOrDefault(x => x.Name == parts[0]);
+                var leafRegistration = Registry.Registrations.FirstOrDefault(x => x.Name == parts[1]);
+                selectedChild = tabbedPage.Children.FirstOrDefault(x =>
+                    x is NavigationPage navPage
+                    && (ViewModelLocator.GetNavigationName(navPage) == parts[0] || (rootRegistration is not null && IsPage(navPage, rootRegistration, parts[0])))
+                    && (ViewModelLocator.GetNavigationName(navPage.RootPage) == parts[1] || (leafRegistration is not null && IsPage(navPage.RootPage, leafRegistration, parts[1]))));
+            }
             else
                 throw new NavigationException($"Invalid Tab Name: {tabName}");
 
@@ -1070,7 +1084,8 @@ private static bool IsPage(Page referencePage, ViewRegistration registration, st
         {
             // We're allowing an empty string here for cases where someone has a manually constructed TabbedPage
             var navigationName = ViewModelLocator.GetNavigationName(referencePage);
-            if (registration.View == referenceType && (string.IsNullOrEmpty(navigationName) || navigationName == name))
+            // registration.Name matches the navigation key (e.g. "Tab2") even when NavigationName still defaults to CLR type name ("Tab2Mock")
+            if (registration.View == referenceType && (string.IsNullOrEmpty(navigationName) || navigationName == name || registration.Name == name))
                 return true;
 
             // This is an override for cases where someone may have a NavigationPage

tests/Maui/Prism.Maui.Tests/Fixtures/Behaviors/EventToCommandBehaviorFixture.cs

@@ -1,5 +1,8 @@
 using System;
+using System.Collections.Generic;
 using System.Globalization;
+using System.Linq;
+using System.Reflection;
 using Microsoft.Maui.Controls;
 using Microsoft.Maui.Controls.Hosting;
 using Microsoft.Maui.Dispatching;
@@ -12,21 +15,43 @@ namespace Prism.Maui.Tests.Fixtures.Behaviors;
 
 public class EventToCommandBehaviorFixture
 {
-    private class ItemTappedEventArgsConverter : IValueConverter
+    /// <summary>Mirrors <see cref="SelectionChangedEventArgs"/> shape for tests (MAUI ctor is not public).</summary>
+    private sealed class FakeSelectionChangedEventArgs : EventArgs
+    {
+        public FakeSelectionChangedEventArgs(IReadOnlyList<object> previousSelection, IReadOnlyList<object> currentSelection)
+        {
+            PreviousSelection = previousSelection;
+            CurrentSelection = currentSelection;
+        }
+
+        public IReadOnlyList<object> PreviousSelection { get; }
+        public IReadOnlyList<object> CurrentSelection { get; }
+    }
+
+    /// <summary>Minimal EventArgs for nested property-path tests (no Item on selection args).</summary>
+    private sealed class TestNestedArgs : EventArgs
+    {
+        public object Item => null;
+    }
+
+    private class SelectionChangedEventArgsConverter : IValueConverter
     {
         private readonly bool _returnParameter;
 
         public bool HasConverted { get; private set; }
 
-        public ItemTappedEventArgsConverter(bool returnParameter)
+        public SelectionChangedEventArgsConverter(bool returnParameter)
         {
             _returnParameter = returnParameter;
         }
 
         public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
         {
             HasConverted = true;
-            return _returnParameter ? parameter : (value as ItemTappedEventArgs)?.Item;
+            if (_returnParameter)
+                return parameter;
+            var prop = value?.GetType().GetRuntimeProperty(nameof(FakeSelectionChangedEventArgs.CurrentSelection));
+            return prop?.GetValue(value) is IReadOnlyList<object> list ? list.FirstOrDefault() : null;
         }
 
         public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
@@ -48,10 +73,10 @@ public void Command_OrderOfExecution()
     {
         const string commandParameter = "ItemProperty";
         var executedCommand = false;
-        var converter = new ItemTappedEventArgsConverter(false);
+        var converter = new SelectionChangedEventArgsConverter(false);
         var behavior = new EventToCommandBehaviorMock
         {
-            EventName = "ItemTapped",
+            EventName = "SelectionChanged",
             EventArgsConverter = converter,
             CommandParameter = commandParameter,
             Command = new DelegateCommand<string>(o =>
@@ -62,9 +87,9 @@ public void Command_OrderOfExecution()
                 Assert.False(converter.HasConverted);
             })
         };
-        var listView = new ListView();
-        listView.Behaviors.Add(behavior);
-        behavior.RaiseEvent(listView, new ItemTappedEventArgs(listView, commandParameter, 0));
+        var collectionView = new CollectionView();
+        collectionView.Behaviors.Add(behavior);
+        behavior.RaiseEvent(collectionView, new FakeSelectionChangedEventArgs(Array.Empty<object>(), new[] { commandParameter }));
         Assert.True(executedCommand);
     }
 
@@ -75,18 +100,18 @@ public void Command_Converter()
         var executedCommand = false;
         var behavior = new EventToCommandBehaviorMock
         {
-            EventName = "ItemTapped",
-            EventArgsConverter = new ItemTappedEventArgsConverter(false),
+            EventName = "SelectionChanged",
+            EventArgsConverter = new SelectionChangedEventArgsConverter(false),
             Command = new DelegateCommand<string>(o =>
             {
                 executedCommand = true;
                 Assert.NotNull(o);
                 Assert.Equal(item, o);
             })
         };
-        var listView = new ListView();
-        listView.Behaviors.Add(behavior);
-        behavior.RaiseEvent(listView, new ItemTappedEventArgs(listView, item, 0));
+        var collectionView = new CollectionView();
+        collectionView.Behaviors.Add(behavior);
+        behavior.RaiseEvent(collectionView, new FakeSelectionChangedEventArgs(Array.Empty<object>(), new[] { item }));
         Assert.True(executedCommand);
     }
 
@@ -97,8 +122,8 @@ public void Command_ConverterWithConverterParameter()
         var executedCommand = false;
         var behavior = new EventToCommandBehaviorMock
         {
-            EventName = "ItemTapped",
-            EventArgsConverter = new ItemTappedEventArgsConverter(true),
+            EventName = "SelectionChanged",
+            EventArgsConverter = new SelectionChangedEventArgsConverter(true),
             EventArgsConverterParameter = item,
             Command = new DelegateCommand<string>(o =>
             {
@@ -107,9 +132,9 @@ public void Command_ConverterWithConverterParameter()
                 Assert.Equal(item, o);
             })
         };
-        var listView = new ListView();
-        listView.Behaviors.Add(behavior);
-        behavior.RaiseEvent(listView, new ItemTappedEventArgs(listView, null, 0));
+        var collectionView = new CollectionView();
+        collectionView.Behaviors.Add(behavior);
+        behavior.RaiseEvent(collectionView, new FakeSelectionChangedEventArgs(Array.Empty<object>(), Array.Empty<object>()));
         Assert.True(executedCommand);
     }
 
@@ -120,7 +145,7 @@ public void Command_ExecuteWithParameter()
         var executedCommand = false;
         var behavior = new EventToCommandBehaviorMock
         {
-            EventName = "ItemTapped",
+            EventName = "SelectionChanged",
             CommandParameter = item,
             Command = new DelegateCommand<string>(o =>
             {
@@ -129,9 +154,9 @@ public void Command_ExecuteWithParameter()
                 Assert.Equal(item, o);
             })
         };
-        var listView = new ListView();
-        listView.Behaviors.Add(behavior);
-        behavior.RaiseEvent(listView, new ItemTappedEventArgs(listView, null, 0));
+        var collectionView = new CollectionView();
+        collectionView.Behaviors.Add(behavior);
+        behavior.RaiseEvent(collectionView, new FakeSelectionChangedEventArgs(Array.Empty<object>(), Array.Empty<object>()));
         Assert.True(executedCommand);
     }
 
@@ -142,18 +167,19 @@ public void Command_EventArgsParameterPath()
         var executedCommand = false;
         var behavior = new EventToCommandBehaviorMock
         {
-            EventName = "ItemTapped",
-            EventArgsParameterPath = "Item",
-            Command = new DelegateCommand<string>(o =>
+            EventName = "SelectionChanged",
+            EventArgsParameterPath = "CurrentSelection",
+            Command = new DelegateCommand<IReadOnlyList<object>>(o =>
             {
                 executedCommand = true;
                 Assert.NotNull(o);
-                Assert.Equal(item, o);
+                Assert.Single(o);
+                Assert.Equal(item, o[0]);
             })
         };
-        var listView = new ListView();
-        listView.Behaviors.Add(behavior);
-        behavior.RaiseEvent(listView, new ItemTappedEventArgs(listView, item, 0));
+        var collectionView = new CollectionView();
+        collectionView.Behaviors.Add(behavior);
+        behavior.RaiseEvent(collectionView, new FakeSelectionChangedEventArgs(Array.Empty<object>(), new[] { item }));
         Assert.True(executedCommand);
     }
 
@@ -167,7 +193,7 @@ public void Command_EventArgsParameterPath()
     //    var executedCommand = false;
     //    var behavior = new EventToCommandBehaviorMock
     //    {
-    //        EventName = "ItemTapped",
+    //        EventName = "SelectionChanged",
     //        EventArgsParameterPath = "Item.AProperty",
     //        Command = new DelegateCommand<object>(o =>
     //        {
@@ -176,9 +202,9 @@ public void Command_EventArgsParameterPath()
     //            Assert.Equal("Value", o);
     //        })
     //    };
-    //    var listView = new ListView();
-    //    listView.Behaviors.Add(behavior);
-    //    behavior.RaiseEvent(listView, new ItemTappedEventArgs(listView, item));
+    //    var collectionView = new CollectionView();
+    //    collectionView.Behaviors.Add(behavior);
+    //    behavior.RaiseEvent(collectionView, new TestNestedArgs());
     //    Assert.True(executedCommand);
     //}
 
@@ -189,17 +215,17 @@ public void Command_EventArgsParameterPath_Nested_When_ChildIsNull()
         var executedCommand = false;
         var behavior = new EventToCommandBehaviorMock
         {
-            EventName = "ItemTapped",
+            EventName = "SelectionChanged",
             EventArgsParameterPath = "Item.AProperty",
             Command = new DelegateCommand<object>(o =>
             {
                 executedCommand = true;
                 Assert.Null(o);
             })
         };
-        var listView = new ListView();
-        listView.Behaviors.Add(behavior);
-        behavior.RaiseEvent(listView, new ItemTappedEventArgs(listView, null, 0));
+        var collectionView = new CollectionView();
+        collectionView.Behaviors.Add(behavior);
+        behavior.RaiseEvent(collectionView, new TestNestedArgs());
         Assert.True(executedCommand);
     }
 
@@ -208,12 +234,12 @@ public void Command_CanExecute()
     {
         var behavior = new EventToCommandBehaviorMock
         {
-            EventName = "ItemTapped",
+            EventName = "SelectionChanged",
             Command = new DelegateCommand(() => Assert.True(false), () => false)
         };
-        var listView = new ListView();
-        listView.Behaviors.Add(behavior);
-        behavior.RaiseEvent(listView, null);
+        var collectionView = new CollectionView();
+        collectionView.Behaviors.Add(behavior);
+        behavior.RaiseEvent(collectionView, null);
     }
 
     [Fact]
@@ -223,17 +249,17 @@ public void Command_CanExecuteWithParameterShouldExecute()
         var executedCommand = false;
         var behavior = new EventToCommandBehaviorMock
         {
-            EventName = "ItemTapped",
+            EventName = "SelectionChanged",
             CommandParameter = shouldExeute,
             Command = new DelegateCommand<string>(o =>
             {
                 executedCommand = true;
                 Assert.True(true);
             }, o => o.Equals(bool.TrueString))
         };
-        var listView = new ListView();
-        listView.Behaviors.Add(behavior);
-        behavior.RaiseEvent(listView, null);
+        var collectionView = new CollectionView();
+        collectionView.Behaviors.Add(behavior);
+        behavior.RaiseEvent(collectionView, null);
         Assert.True(executedCommand);
     }
 
@@ -243,13 +269,13 @@ public void Command_CanExecuteWithParameterShouldNotExeute()
         var shouldExeute = bool.FalseString;
         var behavior = new EventToCommandBehaviorMock
         {
-            EventName = "ItemTapped",
+            EventName = "SelectionChanged",
             CommandParameter = shouldExeute,
             Command = new DelegateCommand<string>(o => Assert.True(false), o => o.Equals(bool.TrueString))
         };
-        var listView = new ListView();
-        listView.Behaviors.Add(behavior);
-        behavior.RaiseEvent(listView, null);
+        var collectionView = new CollectionView();
+        collectionView.Behaviors.Add(behavior);
+        behavior.RaiseEvent(collectionView, null);
     }
 
     [Fact]
@@ -258,16 +284,16 @@ public void Command_Execute()
         var executedCommand = false;
         var behavior = new EventToCommandBehaviorMock
         {
-            EventName = "ItemTapped",
+            EventName = "SelectionChanged",
             Command = new DelegateCommand(() =>
             {
                 executedCommand = true;
                 Assert.True(true);
             })
         };
-        var listView = new ListView();
-        listView.Behaviors.Add(behavior);
-        behavior.RaiseEvent(listView, null);
+        var collectionView = new CollectionView();
+        collectionView.Behaviors.Add(behavior);
+        behavior.RaiseEvent(collectionView, null);
         Assert.True(executedCommand);
     }
 
@@ -276,20 +302,20 @@ public void EventName_InvalidEventShouldThrow()
     {
         var behavior = new EventToCommandBehavior
         {
-            EventName = "OnItemTapped"
+            EventName = "OnSelectionChanged"
         };
-        var listView = new ListView();
-        Assert.Throws<ArgumentException>(() => listView.Behaviors.Add(behavior));
+        var collectionView = new CollectionView();
+        Assert.Throws<ArgumentException>(() => collectionView.Behaviors.Add(behavior));
     }
 
     [Fact]
     public void EventName_Valid()
     {
         var behavior = new EventToCommandBehavior
         {
-            EventName = "ItemTapped"
+            EventName = "SelectionChanged"
         };
-        var listView = new ListView();
-        listView.Behaviors.Add(behavior);
+        var collectionView = new CollectionView();
+        collectionView.Behaviors.Add(behavior);
     }
 }