Add test for navigator_state.restorable_push_replacement.0.dart (#157668)

Contributes to https://github.com/flutter/flutter/issues/130459

It adds a test for
- `examples/api/lib/widgets/navigator/navigator_state.restorable_push_replacement.0.dart`

examples/api/lib/widgets/navigator/navigator_state.restorable_push_replacement.0.dart

@@ -13,14 +13,23 @@ class RestorablePushReplacementExampleApp extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return const MaterialApp(
-      home: RestorablePushReplacementExample(),
+    return const RootRestorationScope(
+      restorationId: 'app',
+      child: MaterialApp(
+        restorationScopeId: 'app',
+        home: RestorablePushReplacementExample(),
+      ),
     );
   }
 }
 
 class RestorablePushReplacementExample extends StatefulWidget {
-  const RestorablePushReplacementExample({super.key});
+  const RestorablePushReplacementExample({
+    this.wasPushed = false,
+    super.key,
+  });
+
+  final bool wasPushed;
 
   @override
   State<RestorablePushReplacementExample> createState() => _RestorablePushReplacementExampleState();
@@ -30,7 +39,9 @@ class _RestorablePushReplacementExampleState extends State<RestorablePushReplace
   @pragma('vm:entry-point')
   static Route<void> _myRouteBuilder(BuildContext context, Object? arguments) {
     return MaterialPageRoute<void>(
-      builder: (BuildContext context) => const RestorablePushReplacementExample(),
+      builder: (BuildContext context) => const RestorablePushReplacementExample(
+        wasPushed: true,
+      ),
     );
   }
 
@@ -40,6 +51,11 @@ class _RestorablePushReplacementExampleState extends State<RestorablePushReplace
       appBar: AppBar(
         title: const Text('Sample Code'),
       ),
+      body: Center(
+        child: widget.wasPushed
+            ? const Text('This is a new route.')
+            : const Text('This is the initial route.'),
+      ),
       floatingActionButton: FloatingActionButton(
         onPressed: () => Navigator.of(context).restorablePushReplacement(
           _myRouteBuilder,

examples/api/test/widgets/navigator/navigator_state.restorable_push_replacement.0_test.dart

@@ -0,0 +1,39 @@
+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+import 'package:flutter_api_samples/widgets/navigator/navigator_state.restorable_push_replacement.0.dart' as example;
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets('It pushes a restorable route and restores it', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const example.RestorablePushReplacementExampleApp(),
+    );
+
+    expect(find.widgetWithText(AppBar, 'Sample Code'), findsOne);
+    expect(find.text('This is the initial route.'), findsOne);
+
+    final TestRestorationData initialData = await tester.getRestorationData();
+
+    await tester.tap(find.widgetWithIcon(FloatingActionButton, Icons.add));
+    await tester.pumpAndSettle();
+
+    expect(find.text('This is a new route.'), findsOne);
+
+    await tester.restartAndRestore();
+
+    expect(find.text('This is a new route.'), findsOne);
+
+    final TestRestorationData pushedData = await tester.getRestorationData();
+
+    await tester.restoreFrom(initialData);
+
+    await tester.pumpAndSettle();
+    expect(find.text('This is the initial route.'), findsOne);
+
+    await tester.restoreFrom(pushedData);
+    expect(find.text('This is a new route.'), findsOne);
+  });
+}