[provider_shopper] Added widget tests for login, catalog and cart screens (#400)

provider_shopper/lib/models/catalog.dart

@@ -12,7 +12,7 @@ import 'package:flutter/material.dart';
 /// For simplicity, the catalog is expected to be immutable (no products are
 /// expected to be added, removed or changed during the execution of the app).
 class CatalogModel {
-  static const _itemNames = [
+  static List<String> itemNames = [
     'Code Smell',
     'Control Flow',
     'Interpreter',
@@ -32,8 +32,8 @@ class CatalogModel {
 
   /// Get item by [id].
   ///
-  /// In this sample, the catalog is infinite, looping over [_itemNames].
-  Item getById(int id) => Item(id, _itemNames[id % _itemNames.length]);
+  /// In this sample, the catalog is infinite, looping over [itemNames].
+  Item getById(int id) => Item(id, itemNames[id % itemNames.length]);
 
   /// Get item by its position in the catalog.
   Item getByPosition(int position) {

provider_shopper/test/cart_widget_test.dart

@@ -0,0 +1,62 @@
+// 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:flutter_test/flutter_test.dart';
+import 'package:provider/provider.dart';
+import 'package:provider_shopper/models/cart.dart';
+import 'package:provider_shopper/models/catalog.dart';
+import 'package:provider_shopper/screens/cart.dart';
+
+CartModel cartModel;
+CatalogModel catalogModel;
+Widget createCartScreen() => MultiProvider(
+      providers: [
+        Provider(create: (context) => CatalogModel()),
+        ChangeNotifierProxyProvider<CatalogModel, CartModel>(
+          create: (context) => CartModel(),
+          update: (context, catalog, cart) {
+            catalogModel = catalog;
+            cartModel = cart;
+            cart.catalog = catalogModel;
+            return cart;
+          },
+        ),
+      ],
+      child: MaterialApp(
+        home: MyCart(),
+      ),
+    );
+
+void main() {
+  group('CartScreen widget tests', () {
+    testWidgets('Tapping BUY button displays snackbar.', (tester) async {
+      await tester.pumpWidget(createCartScreen());
+
+      // Verify no snackbar initially exists.
+      expect(find.byType(SnackBar), findsNothing);
+      await tester.tap(find.text('BUY'));
+      // Schedule animation.
+      await tester.pump();
+      // Verifying the snackbar upon clicking the button.
+      expect(find.byType(SnackBar), findsOneWidget);
+    });
+
+    testWidgets('Testing when the cart contains items', (tester) async {
+      await tester.pumpWidget(createCartScreen());
+
+      // Adding five items in the cart and testing.
+      for (int i = 0; i < 5; i++) {
+        var item = catalogModel.getByPosition(i);
+        cartModel.add(item);
+        await tester.pumpAndSettle();
+        expect(find.text(item.name), findsOneWidget);
+      }
+
+      // Testing total price of the five items.
+      expect(find.text('\$${42 * 5}'), findsOneWidget);
+      expect(find.byIcon(Icons.done), findsNWidgets(5));
+    });
+  });
+}

provider_shopper/test/catalog_widget_test.dart

@@ -0,0 +1,58 @@
+// 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:flutter/widgets.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:provider/provider.dart';
+import 'package:provider_shopper/models/cart.dart';
+import 'package:provider_shopper/models/catalog.dart';
+import 'package:provider_shopper/screens/catalog.dart';
+
+Widget createCatalogScreen() => MultiProvider(
+      providers: [
+        Provider(create: (context) => CatalogModel()),
+        ChangeNotifierProxyProvider<CatalogModel, CartModel>(
+          create: (context) => CartModel(),
+          update: (context, catalog, cart) {
+            cart.catalog = catalog;
+            return cart;
+          },
+        ),
+      ],
+      child: MaterialApp(
+        home: MyCatalog(),
+      ),
+    );
+
+void main() {
+  final catalogListItems = CatalogModel.itemNames.sublist(0, 3);
+
+  group('CatalogScreen Widget Tests', () {
+    testWidgets('Testing item row counts and text', (tester) async {
+      await tester.pumpWidget(createCatalogScreen());
+
+      // Testing for the items on the screen after modifying
+      // the model for a fixed number of items.
+      for (String item in catalogListItems) {
+        expect(find.text(item), findsWidgets);
+      }
+    });
+
+    testWidgets('Testing the ADD buttons and check after clicking',
+        (tester) async {
+      await tester.pumpWidget(createCatalogScreen());
+
+      // Should find ADD buttons on the screen.
+      expect(find.text('ADD'), findsWidgets);
+
+      // Performing the click on the ADD button of the first item in the list.
+      await tester.tap(find.widgetWithText(FlatButton, 'ADD').first);
+      await tester.pumpAndSettle();
+
+      // Verifying if the tapped ADD button has changed to the check icon.
+      expect(find.byIcon(Icons.check), findsOneWidget);
+    });
+  });
+}

provider_shopper/test/login_widget_test.dart

@@ -0,0 +1,41 @@
+// 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:flutter_test/flutter_test.dart';
+import 'package:provider/provider.dart';
+import 'package:provider_shopper/models/cart.dart';
+import 'package:provider_shopper/models/catalog.dart';
+import 'package:provider_shopper/screens/catalog.dart';
+import 'package:provider_shopper/screens/login.dart';
+
+void main() {
+  testWidgets('Login page Widget test', (tester) async {
+    await tester.pumpWidget(MultiProvider(
+      providers: [
+        Provider(create: (context) => CatalogModel()),
+        ChangeNotifierProxyProvider<CatalogModel, CartModel>(
+          create: (context) => CartModel(),
+          update: (context, catalog, cart) {
+            cart.catalog = catalog;
+            return cart;
+          },
+        ),
+      ],
+      child: MaterialApp(
+        initialRoute: '/',
+        routes: {
+          '/': (context) => MyLogin(),
+          '/catalog': (context) => MyCatalog(),
+        },
+      ),
+    ));
+
+    // Verifying the behaviour of ENTER button.
+    await tester.tap(find.text('ENTER'));
+    await tester.pumpAndSettle();
+
+    expect(find.text('Catalog'), findsOneWidget);
+  });
+}