diff --git a/ecommerce_app/lib/src/features/cart/data/local/fake_local_cart_repository.dart b/ecommerce_app/lib/src/features/cart/data/local/fake_local_cart_repository.dart
new file mode 100644
index 00000000..ae24cedb
--- /dev/null
+++ b/ecommerce_app/lib/src/features/cart/data/local/fake_local_cart_repository.dart
@@ -0,0 +1,23 @@
+import 'package:ecommerce_app/src/features/cart/data/local/local_cart_repository.dart';
+import 'package:ecommerce_app/src/features/cart/domain/cart.dart';
+import 'package:ecommerce_app/src/utils/delay.dart';
+import 'package:ecommerce_app/src/utils/in_memory_store.dart';
+
+class FakeLocalCartRepository implements LocalCartRepository {
+  FakeLocalCartRepository({this.addDelay = true});
+  final bool addDelay;
+
+  final _cart = InMemoryStore<Cart>(const Cart());
+
+  @override
+  Future<Cart> fetchCart() => Future.value(_cart.value);
+
+  @override
+  Stream<Cart> watchCart() => _cart.stream;
+
+  @override
+  Future<void> setCart(Cart cart) async {
+    await delay(addDelay);
+    _cart.value = cart;
+  }
+}
diff --git a/ecommerce_app/lib/src/features/cart/data/local/local_cart_repository.dart b/ecommerce_app/lib/src/features/cart/data/local/local_cart_repository.dart
new file mode 100644
index 00000000..bcc4e867
--- /dev/null
+++ b/ecommerce_app/lib/src/features/cart/data/local/local_cart_repository.dart
@@ -0,0 +1,16 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:ecommerce_app/src/features/cart/domain/cart.dart';
+
+/// API for reading, watching and writing local cart data (guest user)
+abstract class LocalCartRepository {
+  Future<Cart> fetchCart();
+
+  Stream<Cart> watchCart();
+
+  Future<void> setCart(Cart cart);
+}
+
+final localCartRepositoryProvider = Provider<LocalCartRepository>((ref) {
+  // * Override this in the main method
+  throw UnimplementedError();
+});
diff --git a/ecommerce_app/lib/src/features/cart/data/remote/fake_remote_cart_repository.dart b/ecommerce_app/lib/src/features/cart/data/remote/fake_remote_cart_repository.dart
new file mode 100644
index 00000000..f54adac7
--- /dev/null
+++ b/ecommerce_app/lib/src/features/cart/data/remote/fake_remote_cart_repository.dart
@@ -0,0 +1,35 @@
+import 'package:ecommerce_app/src/features/cart/data/remote/remote_cart_repository.dart';
+import 'package:ecommerce_app/src/features/cart/domain/cart.dart';
+import 'package:ecommerce_app/src/utils/delay.dart';
+import 'package:ecommerce_app/src/utils/in_memory_store.dart';
+
+class FakeRemoteCartRepository implements RemoteCartRepository {
+  FakeRemoteCartRepository({this.addDelay = true});
+  final bool addDelay;
+
+  /// An InMemoryStore containing the shopping cart data for all users, where:
+  /// key: uid of the user
+  /// value: Cart of that user
+  final _carts = InMemoryStore<Map<String, Cart>>({});
+
+  @override
+  Future<Cart> fetchCart(String uid) {
+    return Future.value(_carts.value[uid] ?? const Cart());
+  }
+
+  @override
+  Stream<Cart> watchCart(String uid) {
+    return _carts.stream.map((cartData) => cartData[uid] ?? const Cart());
+  }
+
+  @override
+  Future<void> setCart(String uid, Cart cart) async {
+    await delay(addDelay);
+    // First, get the current carts data for all users
+    final carts = _carts.value;
+    // Then, set the cart for the given uid
+    carts[uid] = cart;
+    // Finally, update the carts data (will emit a new value)
+    _carts.value = carts;
+  }
+}
diff --git a/ecommerce_app/lib/src/features/cart/data/remote/remote_cart_repository.dart b/ecommerce_app/lib/src/features/cart/data/remote/remote_cart_repository.dart
new file mode 100644
index 00000000..119057c6
--- /dev/null
+++ b/ecommerce_app/lib/src/features/cart/data/remote/remote_cart_repository.dart
@@ -0,0 +1,17 @@
+import 'package:ecommerce_app/src/features/cart/data/remote/fake_remote_cart_repository.dart';
+import 'package:ecommerce_app/src/features/cart/domain/cart.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+/// API for reading, watching and writing cart data for a specific user ID
+abstract class RemoteCartRepository {
+  Future<Cart> fetchCart(String uid);
+
+  Stream<Cart> watchCart(String uid);
+
+  Future<void> setCart(String uid, Cart cart);
+}
+
+final remoteCartRepositoryProvider = Provider<RemoteCartRepository>((ref) {
+  // TODO: replace with "real" remote cart repository
+  return FakeRemoteCartRepository();
+});
diff --git a/ecommerce_app/lib/src/features/cart/domain/mutable_cart.dart b/ecommerce_app/lib/src/features/cart/domain/mutable_cart.dart
index c9a7c978..402c263c 100644
--- a/ecommerce_app/lib/src/features/cart/domain/mutable_cart.dart
+++ b/ecommerce_app/lib/src/features/cart/domain/mutable_cart.dart
@@ -4,45 +4,48 @@ import 'package:ecommerce_app/src/features/products/domain/product.dart';
 
 /// Helper extension used to mutate the items in the shopping cart.
 extension MutableCart on Cart {
+  /// add an item to the cart by *overriding* the quantity if it already exists
+  Cart setItem(Item item) {
+    final copy = Map<ProductID, int>.from(items);
+    copy[item.productId] = item.quantity;
+    return Cart(copy);
+  }
+
+  /// add an item to the cart by *updating* the quantity if it already exists
   Cart addItem(Item item) {
     final copy = Map<ProductID, int>.from(items);
-    if (copy.containsKey(item.productId)) {
-      copy[item.productId] = item.quantity + copy[item.productId]!;
-    } else {
-      copy[item.productId] = item.quantity;
-    }
+    // * update item quantity. Read this for more details:
+    // * https://codewithandrea.com/tips/dart-map-update-method/
+    copy.update(
+      item.productId,
+      // if there is already a value, update it by adding the item quantity
+      (value) => item.quantity + value,
+      // otherwise, add the item with the given quantity
+      ifAbsent: () => item.quantity,
+    );
     return Cart(copy);
   }
 
+  /// add a list of items to the cart by *updating* the quantities of items that
+  /// already exist
   Cart addItems(List<Item> itemsToAdd) {
     final copy = Map<ProductID, int>.from(items);
     for (var item in itemsToAdd) {
-      if (copy.containsKey(item.productId)) {
-        copy[item.productId] = item.quantity + copy[item.productId]!;
-      } else {
-        copy[item.productId] = item.quantity;
-      }
+      copy.update(
+        item.productId,
+        // if there is already a value, update it by adding the item quantity
+        (value) => item.quantity + value,
+        // otherwise, add the item with the given quantity
+        ifAbsent: () => item.quantity,
+      );
     }
     return Cart(copy);
   }
 
+  /// if an item with the given productId is found, remove it
   Cart removeItemById(ProductID productId) {
     final copy = Map<ProductID, int>.from(items);
     copy.remove(productId);
     return Cart(copy);
   }
-
-  Cart updateItemIfExists(Item item) {
-    if (items.containsKey(item.productId)) {
-      final copy = Map<ProductID, int>.from(items);
-      copy[item.productId] = item.quantity;
-      return Cart(copy);
-    } else {
-      return this;
-    }
-  }
-
-  Cart clear() {
-    return const Cart();
-  }
 }
diff --git a/ecommerce_app/lib/src/features/cart/presentation/cart_total/cart_total_text.dart b/ecommerce_app/lib/src/features/cart/presentation/cart_total/cart_total_text.dart
index f7e4a450..7700e334 100644
--- a/ecommerce_app/lib/src/features/cart/presentation/cart_total/cart_total_text.dart
+++ b/ecommerce_app/lib/src/features/cart/presentation/cart_total/cart_total_text.dart
@@ -1,16 +1,17 @@
 import 'package:ecommerce_app/src/utils/currency_formatter.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 /// Text widget for showing the total price of the cart
-class CartTotalText extends StatelessWidget {
+class CartTotalText extends ConsumerWidget {
   const CartTotalText({super.key});
 
   @override
-  Widget build(BuildContext context) {
+  Widget build(BuildContext context, WidgetRef ref) {
     // TODO: Read from data source
     const cartTotal = 104.0;
-    // TODO: Inject formatter
-    final totalFormatted = kCurrencyFormatter.format(cartTotal);
+    final totalFormatted =
+        ref.watch(currencyFormatterProvider).format(cartTotal);
     return Text(
       'Total: $totalFormatted',
       style: Theme.of(context).textTheme.headlineSmall,
diff --git a/ecommerce_app/lib/src/features/cart/presentation/shopping_cart/shopping_cart_item.dart b/ecommerce_app/lib/src/features/cart/presentation/shopping_cart/shopping_cart_item.dart
index 0ee8582e..bf369ef4 100644
--- a/ecommerce_app/lib/src/features/cart/presentation/shopping_cart/shopping_cart_item.dart
+++ b/ecommerce_app/lib/src/features/cart/presentation/shopping_cart/shopping_cart_item.dart
@@ -4,6 +4,7 @@ import 'package:ecommerce_app/src/common_widgets/alert_dialogs.dart';
 import 'package:ecommerce_app/src/common_widgets/async_value_widget.dart';
 import 'package:ecommerce_app/src/features/products/data/fake_products_repository.dart';
 import 'package:ecommerce_app/src/localization/string_hardcoded.dart';
+import 'package:ecommerce_app/src/utils/currency_formatter.dart';
 import 'package:flutter/material.dart';
 import 'package:ecommerce_app/src/common_widgets/custom_image.dart';
 import 'package:ecommerce_app/src/common_widgets/item_quantity_selector.dart';
@@ -12,7 +13,6 @@ import 'package:ecommerce_app/src/constants/app_sizes.dart';
 import 'package:ecommerce_app/src/features/cart/domain/item.dart';
 import 'package:ecommerce_app/src/features/products/domain/product.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
-import 'package:intl/intl.dart';
 
 /// Shows a shopping cart item (or loading/error UI if needed)
 class ShoppingCartItem extends ConsumerWidget {
@@ -54,7 +54,7 @@ class ShoppingCartItem extends ConsumerWidget {
 }
 
 /// Shows a shopping cart item for a given product
-class ShoppingCartItemContents extends StatelessWidget {
+class ShoppingCartItemContents extends ConsumerWidget {
   const ShoppingCartItemContents({
     super.key,
     required this.product,
@@ -71,10 +71,9 @@ class ShoppingCartItemContents extends StatelessWidget {
   static Key deleteKey(int index) => Key('delete-$index');
 
   @override
-  Widget build(BuildContext context) {
-    // TODO: error handling
-    // TODO: Inject formatter
-    final priceFormatted = NumberFormat.simpleCurrency().format(product.price);
+  Widget build(BuildContext context, WidgetRef ref) {
+    final priceFormatted =
+        ref.watch(currencyFormatterProvider).format(product.price);
     return ResponsiveTwoColumnLayout(
       startFlex: 1,
       endFlex: 2,
@@ -90,28 +89,10 @@ class ShoppingCartItemContents extends StatelessWidget {
           gapH24,
           isEditable
               // show the quantity selector and a delete button
-              ? Row(
-                  mainAxisAlignment: MainAxisAlignment.spaceBetween,
-                  children: [
-                    ItemQuantitySelector(
-                      quantity: item.quantity,
-                      maxQuantity: min(product.availableQuantity, 10),
-                      itemIndex: itemIndex,
-                      // TODO: Implement onChanged
-                      onChanged: (value) {
-                        showNotImplementedAlertDialog(context: context);
-                      },
-                    ),
-                    IconButton(
-                      key: deleteKey(itemIndex),
-                      icon: Icon(Icons.delete, color: Colors.red[700]),
-                      // TODO: Implement onPressed
-                      onPressed: () {
-                        showNotImplementedAlertDialog(context: context);
-                      },
-                    ),
-                    const Spacer(),
-                  ],
+              ? EditOrRemoveItemWidget(
+                  product: product,
+                  item: item,
+                  itemIndex: itemIndex,
                 )
               // else, show the quantity as a read-only label
               : Padding(
@@ -125,3 +106,46 @@ class ShoppingCartItemContents extends StatelessWidget {
     );
   }
 }
+
+// custom widget to show the quantity selector and a delete button
+class EditOrRemoveItemWidget extends ConsumerWidget {
+  const EditOrRemoveItemWidget({
+    super.key,
+    required this.product,
+    required this.item,
+    required this.itemIndex,
+  });
+  final Product product;
+  final Item item;
+  final int itemIndex;
+
+  // * Keys for testing using find.byKey()
+  static Key deleteKey(int index) => Key('delete-$index');
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return Row(
+      mainAxisAlignment: MainAxisAlignment.spaceBetween,
+      children: [
+        ItemQuantitySelector(
+          quantity: item.quantity,
+          maxQuantity: min(product.availableQuantity, 10),
+          itemIndex: itemIndex,
+          // TODO: Implement onChanged
+          onChanged: (value) {
+            showNotImplementedAlertDialog(context: context);
+          },
+        ),
+        IconButton(
+          key: deleteKey(itemIndex),
+          icon: Icon(Icons.delete, color: Colors.red[700]),
+          // TODO: Implement onPressed
+          onPressed: () {
+            showNotImplementedAlertDialog(context: context);
+          },
+        ),
+        const Spacer(),
+      ],
+    );
+  }
+}
diff --git a/ecommerce_app/lib/src/features/cart/presentation/shopping_cart/shopping_cart_screen.dart b/ecommerce_app/lib/src/features/cart/presentation/shopping_cart/shopping_cart_screen.dart
index b6e1aa1b..168d7a60 100644
--- a/ecommerce_app/lib/src/features/cart/presentation/shopping_cart/shopping_cart_screen.dart
+++ b/ecommerce_app/lib/src/features/cart/presentation/shopping_cart/shopping_cart_screen.dart
@@ -14,6 +14,7 @@ class ShoppingCartScreen extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    // TODO: error handling
     // TODO: Read from data source
     const cartItemsList = [
       Item(
diff --git a/ecommerce_app/lib/src/features/orders/presentation/orders_list/order_card.dart b/ecommerce_app/lib/src/features/orders/presentation/orders_list/order_card.dart
index ba7d2c0d..3d624d77 100644
--- a/ecommerce_app/lib/src/features/orders/presentation/orders_list/order_card.dart
+++ b/ecommerce_app/lib/src/features/orders/presentation/orders_list/order_card.dart
@@ -7,6 +7,7 @@ import 'package:ecommerce_app/src/features/cart/domain/item.dart';
 import 'package:ecommerce_app/src/features/orders/domain/order.dart';
 import 'package:ecommerce_app/src/utils/currency_formatter.dart';
 import 'package:ecommerce_app/src/utils/date_formatter.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 /// Shows all the details for a given order
 class OrderCard extends StatelessWidget {
@@ -35,16 +36,16 @@ class OrderCard extends StatelessWidget {
 /// Order header showing the following:
 /// - Total order amount
 /// - Order date
-class OrderHeader extends StatelessWidget {
+class OrderHeader extends ConsumerWidget {
   const OrderHeader({super.key, required this.order});
   final Order order;
 
   @override
-  Widget build(BuildContext context) {
-    // TODO: Inject currency formatter
-    final totalFormatted = kCurrencyFormatter.format(order.total);
-    // TODO: Inject date formatter
-    final dateFormatted = kDateFormatter.format(order.orderDate);
+  Widget build(BuildContext context, WidgetRef ref) {
+    final totalFormatted =
+        ref.watch(currencyFormatterProvider).format(order.total);
+    final dateFormatted =
+        ref.watch(dateFormatterProvider).format(order.orderDate);
     return Container(
       color: Colors.grey[200],
       padding: const EdgeInsets.all(Sizes.p16),
diff --git a/ecommerce_app/lib/src/features/products/data/fake_products_repository.dart b/ecommerce_app/lib/src/features/products/data/fake_products_repository.dart
index 63a1a731..1e10eed3 100644
--- a/ecommerce_app/lib/src/features/products/data/fake_products_repository.dart
+++ b/ecommerce_app/lib/src/features/products/data/fake_products_repository.dart
@@ -40,7 +40,8 @@ class FakeProductsRepository {
 }
 
 final productsRepositoryProvider = Provider<FakeProductsRepository>((ref) {
-  return FakeProductsRepository();
+  // * Set addDelay to false for faster loading
+  return FakeProductsRepository(addDelay: false);
 });
 
 final productsListStreamProvider =
diff --git a/ecommerce_app/lib/src/features/products/presentation/home_app_bar/shopping_cart_icon.dart b/ecommerce_app/lib/src/features/products/presentation/home_app_bar/shopping_cart_icon.dart
index d421bf54..c83f37d5 100644
--- a/ecommerce_app/lib/src/features/products/presentation/home_app_bar/shopping_cart_icon.dart
+++ b/ecommerce_app/lib/src/features/products/presentation/home_app_bar/shopping_cart_icon.dart
@@ -1,17 +1,18 @@
 import 'package:ecommerce_app/src/routing/app_router.dart';
 import 'package:flutter/material.dart';
 import 'package:ecommerce_app/src/constants/app_sizes.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
 
 /// Shopping cart icon with items count badge
-class ShoppingCartIcon extends StatelessWidget {
+class ShoppingCartIcon extends ConsumerWidget {
   const ShoppingCartIcon({super.key});
 
   // * Keys for testing using find.byKey()
   static const shoppingCartIconKey = Key('shopping-cart');
 
   @override
-  Widget build(BuildContext context) {
+  Widget build(BuildContext context, WidgetRef ref) {
     // TODO: Read from data source
     const cartItemsCount = 3;
     return Stack(
diff --git a/ecommerce_app/lib/src/features/products/presentation/product_screen/leave_review_action.dart b/ecommerce_app/lib/src/features/products/presentation/product_screen/leave_review_action.dart
index f90bb10f..4db54cd5 100644
--- a/ecommerce_app/lib/src/features/products/presentation/product_screen/leave_review_action.dart
+++ b/ecommerce_app/lib/src/features/products/presentation/product_screen/leave_review_action.dart
@@ -6,22 +6,23 @@ import 'package:flutter/material.dart';
 import 'package:ecommerce_app/src/common_widgets/custom_text_button.dart';
 import 'package:ecommerce_app/src/common_widgets/responsive_two_column_layout.dart';
 import 'package:ecommerce_app/src/constants/app_sizes.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
 
 /// Simple widget to show the product purchase date along with a button to
 /// leave a review.
-class LeaveReviewAction extends StatelessWidget {
+class LeaveReviewAction extends ConsumerWidget {
   const LeaveReviewAction({super.key, required this.productId});
   final String productId;
 
   @override
-  Widget build(BuildContext context) {
+  Widget build(BuildContext context, WidgetRef ref) {
     // TODO: Read from data source
     final purchase = Purchase(orderId: 'abc', orderDate: DateTime.now());
     // ignore: unnecessary_null_comparison
     if (purchase != null) {
-      // TODO: Inject date formatter
-      final dateFormatted = kDateFormatter.format(purchase.orderDate);
+      final dateFormatted =
+          ref.watch(dateFormatterProvider).format(purchase.orderDate);
       return Column(
         children: [
           const Divider(),
diff --git a/ecommerce_app/lib/src/features/products/presentation/product_screen/product_screen.dart b/ecommerce_app/lib/src/features/products/presentation/product_screen/product_screen.dart
index ca4f8acd..5bea4236 100644
--- a/ecommerce_app/lib/src/features/products/presentation/product_screen/product_screen.dart
+++ b/ecommerce_app/lib/src/features/products/presentation/product_screen/product_screen.dart
@@ -53,13 +53,14 @@ class ProductScreen extends StatelessWidget {
 /// Shows all the product details along with actions to:
 /// - leave a review
 /// - add to cart
-class ProductDetails extends StatelessWidget {
+class ProductDetails extends ConsumerWidget {
   const ProductDetails({super.key, required this.product});
   final Product product;
 
   @override
-  Widget build(BuildContext context) {
-    final priceFormatted = kCurrencyFormatter.format(product.price);
+  Widget build(BuildContext context, WidgetRef ref) {
+    final priceFormatted =
+        ref.watch(currencyFormatterProvider).format(product.price);
     return ResponsiveTwoColumnLayout(
       startContent: Card(
         child: Padding(
diff --git a/ecommerce_app/lib/src/features/products/presentation/products_list/product_card.dart b/ecommerce_app/lib/src/features/products/presentation/products_list/product_card.dart
index b50a468f..1a7ec6d9 100644
--- a/ecommerce_app/lib/src/features/products/presentation/products_list/product_card.dart
+++ b/ecommerce_app/lib/src/features/products/presentation/products_list/product_card.dart
@@ -5,9 +5,10 @@ import 'package:ecommerce_app/src/common_widgets/custom_image.dart';
 import 'package:ecommerce_app/src/constants/app_sizes.dart';
 import 'package:ecommerce_app/src/features/products/domain/product.dart';
 import 'package:ecommerce_app/src/utils/currency_formatter.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 /// Used to show a single product inside a card.
-class ProductCard extends StatelessWidget {
+class ProductCard extends ConsumerWidget {
   const ProductCard({super.key, required this.product, this.onPressed});
   final Product product;
   final VoidCallback? onPressed;
@@ -16,9 +17,9 @@ class ProductCard extends StatelessWidget {
   static const productCardKey = Key('product-card');
 
   @override
-  Widget build(BuildContext context) {
-    // TODO: Inject formatter
-    final priceFormatted = kCurrencyFormatter.format(product.price);
+  Widget build(BuildContext context, WidgetRef ref) {
+    final priceFormatted =
+        ref.watch(currencyFormatterProvider).format(product.price);
     return Card(
       child: InkWell(
         key: productCardKey,
diff --git a/ecommerce_app/lib/src/features/reviews/presentation/product_reviews/product_review_card.dart b/ecommerce_app/lib/src/features/reviews/presentation/product_reviews/product_review_card.dart
index 5040db78..8c6e2507 100644
--- a/ecommerce_app/lib/src/features/reviews/presentation/product_reviews/product_review_card.dart
+++ b/ecommerce_app/lib/src/features/reviews/presentation/product_reviews/product_review_card.dart
@@ -4,15 +4,15 @@ import 'package:flutter/material.dart';
 import 'package:ecommerce_app/src/constants/app_sizes.dart';
 import 'package:ecommerce_app/src/features/reviews/domain/review.dart';
 import 'package:ecommerce_app/src/utils/date_formatter.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 /// Simple card widget to show a product review info (score, comment, date)
-class ProductReviewCard extends StatelessWidget {
+class ProductReviewCard extends ConsumerWidget {
   const ProductReviewCard(this.review, {super.key});
   final Review review;
   @override
-  Widget build(BuildContext context) {
-    // TODO: Inject date formatter
-    final dateFormatted = kDateFormatter.format(review.date);
+  Widget build(BuildContext context, WidgetRef ref) {
+    final dateFormatted = ref.watch(dateFormatterProvider).format(review.date);
     return Card(
       child: Padding(
         padding: const EdgeInsets.all(Sizes.p16),
diff --git a/ecommerce_app/lib/src/utils/currency_formatter.dart b/ecommerce_app/lib/src/utils/currency_formatter.dart
index 7de90c68..6a5027f5 100644
--- a/ecommerce_app/lib/src/utils/currency_formatter.dart
+++ b/ecommerce_app/lib/src/utils/currency_formatter.dart
@@ -1,4 +1,9 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:intl/intl.dart';
 
-/// Currency formatter to be used in the app.
-final kCurrencyFormatter = NumberFormat.simpleCurrency();
+final currencyFormatterProvider = Provider<NumberFormat>((ref) {
+  /// Currency formatter to be used in the app.
+  /// * en_US is hardcoded to ensure all prices show with a dollar sign ($)
+  /// * This may or may not be what you want in your own apps.
+  return NumberFormat.simpleCurrency(locale: "en_US");
+});
diff --git a/ecommerce_app/lib/src/utils/date_formatter.dart b/ecommerce_app/lib/src/utils/date_formatter.dart
index 0145f913..48d3e059 100644
--- a/ecommerce_app/lib/src/utils/date_formatter.dart
+++ b/ecommerce_app/lib/src/utils/date_formatter.dart
@@ -1,4 +1,7 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:intl/intl.dart';
 
-/// Date formatter to be used in the app.
-final kDateFormatter = DateFormat.MMMEd();
+final dateFormatterProvider = Provider<DateFormat>((ref) {
+  /// Date formatter to be used in the app.
+  return DateFormat.MMMEd();
+});
diff --git a/ecommerce_app/pubspec.lock b/ecommerce_app/pubspec.lock
index 5f35b39a..21ca45d1 100644
--- a/ecommerce_app/pubspec.lock
+++ b/ecommerce_app/pubspec.lock
@@ -227,10 +227,10 @@ packages:
     dependency: transitive
     description:
       name: lints
-      sha256: "4a16b3f03741e1252fda5de3ce712666d010ba2122f8e912c94f9f7b90e1a4c3"
+      sha256: "3315600f3fb3b135be672bf4a178c55f274bebe368325ae18462c89ac1e3b413"
       url: "https://pub.dev"
     source: hosted
-    version: "5.1.0"
+    version: "5.0.0"
   logging:
     dependency: transitive
     description:
@@ -445,5 +445,5 @@ packages:
     source: hosted
     version: "3.1.2"
 sdks:
-  dart: ">=3.6.0-0 <4.0.0"
+  dart: ">=3.5.0 <4.0.0"
   flutter: ">=3.19.0"
diff --git a/ecommerce_app/test/src/features/cart/domain/mutable_cart_test.dart b/ecommerce_app/test/src/features/cart/domain/mutable_cart_test.dart
new file mode 100644
index 00000000..8014ea33
--- /dev/null
+++ b/ecommerce_app/test/src/features/cart/domain/mutable_cart_test.dart
@@ -0,0 +1,108 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:ecommerce_app/src/features/cart/domain/cart.dart';
+import 'package:ecommerce_app/src/features/cart/domain/item.dart';
+import 'package:ecommerce_app/src/features/cart/domain/mutable_cart.dart';
+
+void main() {
+  group('set item', () {
+    test('empty cart - set item with quantity', () {
+      final cart =
+          const Cart().setItem(const Item(productId: '1', quantity: 2));
+      expect(cart.items, {'1': 2});
+    });
+    test('cart with same item - override quantity', () {
+      final cart = const Cart()
+          .addItem(const Item(productId: '1', quantity: 1))
+          .setItem(const Item(productId: '1', quantity: 2));
+      expect(cart.items, {'1': 2});
+    });
+    test('cart with different item - set item with quantity', () {
+      final cart = const Cart()
+          .addItem(const Item(productId: '2', quantity: 1))
+          .setItem(const Item(productId: '1', quantity: 2));
+      expect(cart.items, {
+        '2': 1,
+        '1': 2,
+      });
+    });
+  });
+
+  group('add item', () {
+    test('empty cart - add item', () {
+      final cart =
+          const Cart().addItem(const Item(productId: '1', quantity: 1));
+      expect(cart.items, {'1': 1});
+    });
+    test('empty cart - add two items', () {
+      final cart = const Cart()
+          .addItem(const Item(productId: '1', quantity: 1))
+          .addItem(const Item(productId: '2', quantity: 1));
+      expect(cart.items, {
+        '1': 1,
+        '2': 1,
+      });
+    });
+    test('empty cart - add same item twice', () {
+      final cart = const Cart()
+          .addItem(const Item(productId: '1', quantity: 1))
+          .addItem(const Item(productId: '1', quantity: 1));
+      expect(cart.items, {'1': 2});
+    });
+  });
+
+  group('add items', () {
+    test('empty cart - add two items', () {
+      final cart = const Cart().addItems([
+        const Item(productId: '1', quantity: 1),
+        const Item(productId: '2', quantity: 1),
+      ]);
+      expect(cart.items, {
+        '1': 1,
+        '2': 1,
+      });
+    });
+    test('cart with one item - add two items of which one matching', () {
+      final cart = const Cart()
+          .addItem(const Item(productId: '1', quantity: 1))
+          .addItems([
+        const Item(productId: '1', quantity: 1),
+        const Item(productId: '2', quantity: 1),
+      ]);
+      expect(cart.items, {
+        '1': 2,
+        '2': 1,
+      });
+    });
+    test('cart with one item - add two new items', () {
+      final cart = const Cart()
+          .addItem(const Item(productId: '1', quantity: 1))
+          .addItems([
+        const Item(productId: '2', quantity: 1),
+        const Item(productId: '3', quantity: 1),
+      ]);
+      expect(cart.items, {
+        '1': 1,
+        '2': 1,
+        '3': 1,
+      });
+    });
+  });
+  group('remove item', () {
+    test('empty cart - remove item', () {
+      final cart = const Cart().removeItemById('1');
+      expect(cart.items, {});
+    });
+    test('empty cart - remove matching item', () {
+      final cart = const Cart()
+          .addItem(const Item(productId: '1', quantity: 1))
+          .removeItemById('1');
+      expect(cart.items, {});
+    });
+    test('empty cart - remove non-matching item', () {
+      final cart = const Cart()
+          .addItem(const Item(productId: '2', quantity: 1))
+          .removeItemById('1');
+      expect(cart.items, {'2': 1});
+    });
+  });
+}
diff --git a/ecommerce_app/test/src/mocks.dart b/ecommerce_app/test/src/mocks.dart
index 33a1c527..23595384 100644
--- a/ecommerce_app/test/src/mocks.dart
+++ b/ecommerce_app/test/src/mocks.dart
@@ -1,4 +1,10 @@
 import 'package:ecommerce_app/src/features/authentication/data/fake_auth_repository.dart';
+import 'package:ecommerce_app/src/features/cart/data/local/local_cart_repository.dart';
+import 'package:ecommerce_app/src/features/cart/data/remote/remote_cart_repository.dart';
 import 'package:mocktail/mocktail.dart';
 
 class MockAuthRepository extends Mock implements FakeAuthRepository {}
+
+class MockRemoteCartRepository extends Mock implements RemoteCartRepository {}
+
+class MockLocalCartRepository extends Mock implements LocalCartRepository {}