Testing sample (#500)

testing_app/test/models/favorites_test.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 'dart:math';
+import 'package:test/test.dart';
+import 'package:testing_app/models/favorites.dart';
+
+void main() {
+  group('Testing App Provider Tests', () {
+    // Create an object of the provider.
+    var favorites = Favorites();
+
+    test('A new item should be added', () {
+      // Generate a random number.
+      var number = Random().nextInt(50);
+
+      // Add the number to the list.
+      favorites.add(number);
+
+      // Verify if the number was inserted.
+      expect(favorites.items.contains(number), true);
+    });
+
+    test('An item should be removed', () {
+      // Generate a random number.
+      var number = Random().nextInt(50);
+
+      // Add the number to the list.
+      favorites.add(number);
+
+      // Verify if the number was inserted.
+      expect(favorites.items.contains(number), true);
+
+      // Remove the number from the list.
+      favorites.remove(number);
+
+      // Verify if the number was removed successfully.
+      expect(favorites.items.contains(number), false);
+    });
+  });
+}