Testing sample (#500)

testing_app/lib/main.dart

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+// Copyright 2020 The Flutter team. 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:provider/provider.dart';
+import 'package:testing_app/models/favorites.dart';
+import 'package:testing_app/screens/favorites.dart';
+import 'package:testing_app/screens/home.dart';
+
+void main() {
+  runApp(TestingApp());
+}
+
+class TestingApp extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    return ChangeNotifierProvider<Favorites>(
+      create: (context) => Favorites(),
+      child: MaterialApp(
+        title: 'Testing Sample',
+        theme: ThemeData(
+          primarySwatch: Colors.blue,
+          visualDensity: VisualDensity.adaptivePlatformDensity,
+        ),
+        routes: {
+          HomePage.routeName: (context) => HomePage(),
+          FavoritesPage.routeName: (context) => FavoritesPage(),
+        },
+        initialRoute: HomePage.routeName,
+      ),
+    );
+  }
+}

testing_app/lib/models/favorites.dart

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+// Copyright 2020 The Flutter team. 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';
+
+/// The [Favorites] class holds a list of favorite items saved by the user.
+class Favorites extends ChangeNotifier {
+  final List<int> _favoriteItems = [];
+
+  List<int> get items => _favoriteItems;
+
+  void add(int itemNo) {
+    _favoriteItems.add(itemNo);
+    notifyListeners();
+  }
+
+  void remove(int itemNo) {
+    _favoriteItems.remove(itemNo);
+    notifyListeners();
+  }
+}

testing_app/lib/screens/favorites.dart

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+// Copyright 2020 The Flutter team. 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:provider/provider.dart';
+import 'package:testing_app/models/favorites.dart';
+
+class FavoritesPage extends StatelessWidget {
+  static String routeName = '/favorites_page';
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: Text('Favorites'),
+      ),
+      body: Consumer<Favorites>(
+        builder: (context, value, child) => ListView.builder(
+          itemCount: value.items.length,
+          padding: const EdgeInsets.symmetric(vertical: 16),
+          itemBuilder: (context, index) => FavoriteItemTile(value.items[index]),
+        ),
+      ),
+    );
+  }
+}
+
+class FavoriteItemTile extends StatelessWidget {
+  final int itemNo;
+
+  const FavoriteItemTile(
+    this.itemNo,
+  );
+
+  @override
+  Widget build(BuildContext context) {
+    return Padding(
+      padding: const EdgeInsets.all(8.0),
+      child: ListTile(
+        leading: CircleAvatar(
+          backgroundColor: Colors.primaries[itemNo % Colors.primaries.length],
+        ),
+        title: Text(
+          'Item $itemNo',
+          key: Key('favorites_text_$itemNo'),
+        ),
+        trailing: IconButton(
+          key: Key('remove_icon_$itemNo'),
+          icon: Icon(Icons.close),
+          onPressed: () {
+            Provider.of<Favorites>(context, listen: false).remove(itemNo);
+            Scaffold.of(context).showSnackBar(
+              SnackBar(
+                content: Text('Removed from favorites.'),
+                duration: Duration(seconds: 1),
+              ),
+            );
+          },
+        ),
+      ),
+    );
+  }
+}

testing_app/lib/screens/home.dart

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+// Copyright 2020 The Flutter team. 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:provider/provider.dart';
+import 'package:testing_app/models/favorites.dart';
+import 'package:testing_app/screens/favorites.dart';
+
+class HomePage extends StatelessWidget {
+  static String routeName = '/';
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: Text('Testing Sample'),
+        actions: <Widget>[
+          FlatButton.icon(
+            textColor: Colors.white,
+            onPressed: () {
+              Navigator.pushNamed(context, FavoritesPage.routeName);
+            },
+            icon: Icon(Icons.favorite_border),
+            label: Text('Favorites'),
+          ),
+        ],
+      ),
+      body: ListView.builder(
+        itemCount: 100,
+        cacheExtent: 20.0,
+        padding: const EdgeInsets.symmetric(vertical: 16),
+        itemBuilder: (context, index) => ItemTile(index),
+      ),
+    );
+  }
+}
+
+class ItemTile extends StatelessWidget {
+  final int itemNo;
+
+  const ItemTile(
+    this.itemNo,
+  );
+
+  @override
+  Widget build(BuildContext context) {
+    var favoritesList = Provider.of<Favorites>(context);
+
+    return Padding(
+      padding: const EdgeInsets.all(8.0),
+      child: ListTile(
+        leading: CircleAvatar(
+          backgroundColor: Colors.primaries[itemNo % Colors.primaries.length],
+        ),
+        title: Text(
+          'Item $itemNo',
+          key: Key('text_$itemNo'),
+        ),
+        trailing: IconButton(
+          key: Key('icon_$itemNo'),
+          icon: favoritesList.items.contains(itemNo)
+              ? Icon(Icons.favorite)
+              : Icon(Icons.favorite_border),
+          onPressed: () {
+            !favoritesList.items.contains(itemNo)
+                ? favoritesList.add(itemNo)
+                : favoritesList.remove(itemNo);
+            Scaffold.of(context).showSnackBar(
+              SnackBar(
+                content: Text(favoritesList.items.contains(itemNo)
+                    ? 'Added to favorites.'
+                    : 'Removed from favorites.'),
+                duration: Duration(seconds: 1),
+              ),
+            );
+          },
+        ),
+      ),
+    );
+  }
+}