Testing sample (#500)

testing_app/test/favorites_test.dart

@@ -0,0 +1,65 @@
+// 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 'dart:math';
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:provider/provider.dart';
+import 'package:testing_app/models/favorites.dart';
+import 'package:testing_app/screens/favorites.dart';
+
+Favorites favoritesList;
+
+Widget createFavoritesScreen() => ChangeNotifierProvider<Favorites>(
+      create: (context) {
+        favoritesList = Favorites();
+        return favoritesList;
+      },
+      child: MaterialApp(
+        home: FavoritesPage(),
+      ),
+    );
+
+void addRandomItems() {
+  for (var i = 0; i < 5; i++) {
+    favoritesList.add(Random().nextInt(50));
+  }
+}
+
+void main() {
+  group('Favorites Page Widget Tests', () {
+    testWidgets('Test if ListView shows up', (tester) async {
+      await tester.pumpWidget(createFavoritesScreen());
+
+      // Add random values.
+      addRandomItems();
+      await tester.pumpAndSettle();
+
+      // Verify if ListView shows up.
+      expect(find.byType(ListView), findsOneWidget);
+    });
+
+    testWidgets('Testing Remove Button', (tester) async {
+      await tester.pumpWidget(createFavoritesScreen());
+
+      // Add random values.
+      addRandomItems();
+      await tester.pumpAndSettle();
+
+      // Get the total number of items available.
+      var totalItems = tester.widgetList(find.byIcon(Icons.close)).length;
+
+      // Remove one item.
+      await tester.tap(find.byIcon(Icons.close).first);
+      await tester.pumpAndSettle();
+
+      // Check if removed properly.
+      expect(tester.widgetList(find.byIcon(Icons.close)).length,
+          lessThan(totalItems));
+
+      // Verify if the appropriate message is shown.
+      expect(find.text('Removed from favorites.'), findsOneWidget);
+    });
+  });
+}