[testing_app] added basic placeholder for favorites list (#581)

testing_app/lib/screens/favorites.dart

@@ -16,10 +16,15 @@ class FavoritesPage extends StatelessWidget {
         title: Text('Favorites'),
       ),
       body: Consumer<Favorites>(
-        builder: (context, value, child) => ListView.builder(
+        builder: (context, value, child) => value.items.isNotEmpty
+            ? ListView.builder(
                 itemCount: value.items.length,
                 padding: const EdgeInsets.symmetric(vertical: 16),
-          itemBuilder: (context, index) => FavoriteItemTile(value.items[index]),
+                itemBuilder: (context, index) =>
+                    FavoriteItemTile(value.items[index]),
+              )
+            : Center(
+                child: Text('No favorites added.'),
               ),
       ),
     );

testing_app/test/favorites_test.dart

@@ -28,6 +28,14 @@ void addItems() {
 
 void main() {
   group('Favorites Page Widget Tests', () {
+    testWidgets('Test if Placeholder shows in case of empty list',
+        (tester) async {
+      await tester.pumpWidget(createFavoritesScreen());
+
+      // Verify if the placeholder text shows up.
+      expect(find.text('No favorites added.'), findsOneWidget);
+    });
+
     testWidgets('Test if ListView shows up', (tester) async {
       await tester.pumpWidget(createFavoritesScreen());
 

testing_app/test/models/favorites_test.dart

@@ -11,7 +11,6 @@ void main() {
     var favorites = Favorites();
 
     test('A new item should be added', () {
-      // Generate a random number.
       var number = 35;
 
       // Add the number to the list.
@@ -22,7 +21,6 @@ void main() {
     });
 
     test('An item should be removed', () {
-      // Generate a random number.
       var number = 45;
 
       // Add the number to the list.