diff --git a/pubspec.lock b/pubspec.lock
index b930472..bae0bc8 100644
--- a/pubspec.lock
+++ b/pubspec.lock
@@ -600,6 +600,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "2.0.0"
+  mocktail:
+    dependency: "direct dev"
+    description:
+      name: mocktail
+      sha256: "5e1bf53cc7baa8062a33b84424deb61513858ea05c601b8509e683815b5914aa"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.0.5"
   native_toolchain_c:
     dependency: transitive
     description:
diff --git a/pubspec.yaml b/pubspec.yaml
index 6368ea0..3e5747d 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -65,6 +65,7 @@ dev_dependencies:
   flutter_lints: ^6.0.0
   drift_dev: ^2.34.2+1
   build_runner: ^2.15.0
+  mocktail: ^1.0.4
 
 # For information on the generic Dart part of this file, see the
 # following page: https://dart.dev/tools/pub/pubspec
diff --git a/test/bar_tab_model_test.dart b/test/bar_tab_model_test.dart
new file mode 100644
index 0000000..b49dfdb
--- /dev/null
+++ b/test/bar_tab_model_test.dart
@@ -0,0 +1,142 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:kooltab2/models/bar_tab.dart';
+import 'package:kooltab2/models/tab_item.dart';
+
+void main() {
+  group('BarTab', () {
+    group('totalInCents', () {
+      test('calculates total from items', () {
+        final tab = BarTab(
+          id: 'tab-1',
+          customerName: 'John',
+          status: 'open',
+          openedAt: DateTime.now(),
+          items: [
+            const TabItem(
+              id: 'item-1',
+              tabId: 'tab-1',
+              productId: 'prod-1',
+              productName: 'Beer',
+              quantity: 2,
+              unitPriceInCents: 400,
+            ),
+            const TabItem(
+              id: 'item-2',
+              tabId: 'tab-1',
+              productId: 'prod-2',
+              productName: 'Wine',
+              quantity: 1,
+              unitPriceInCents: 600,
+            ),
+          ],
+        );
+
+        expect(tab.totalInCents, 1400);
+      });
+
+      test('returns 0 for empty tab', () {
+        final tab = BarTab(
+          id: 'tab-1',
+          customerName: 'John',
+          status: 'open',
+          openedAt: DateTime.now(),
+          items: const [],
+        );
+
+        expect(tab.totalInCents, 0);
+      });
+    });
+
+    group('itemCount', () {
+      test('sums quantities of all items', () {
+        final tab = BarTab(
+          id: 'tab-1',
+          customerName: 'John',
+          status: 'open',
+          openedAt: DateTime.now(),
+          items: [
+            const TabItem(
+              id: 'item-1',
+              tabId: 'tab-1',
+              productId: 'prod-1',
+              productName: 'Beer',
+              quantity: 3,
+              unitPriceInCents: 400,
+            ),
+            const TabItem(
+              id: 'item-2',
+              tabId: 'tab-1',
+              productId: 'prod-2',
+              productName: 'Wine',
+              quantity: 2,
+              unitPriceInCents: 600,
+            ),
+          ],
+        );
+
+        expect(tab.itemCount, 5);
+      });
+
+      test('returns 0 for empty tab', () {
+        final tab = BarTab(
+          id: 'tab-1',
+          customerName: 'John',
+          status: 'open',
+          openedAt: DateTime.now(),
+          items: const [],
+        );
+
+        expect(tab.itemCount, 0);
+      });
+    });
+
+    group('formattedTotal', () {
+      test('formats total with euro symbol', () {
+        final tab = BarTab(
+          id: 'tab-1',
+          customerName: 'John',
+          status: 'open',
+          openedAt: DateTime.now(),
+          items: const [
+            TabItem(
+              id: 'item-1',
+              tabId: 'tab-1',
+              productId: 'prod-1',
+              productName: 'Beer',
+              quantity: 2,
+              unitPriceInCents: 425,
+            ),
+          ],
+        );
+
+        expect(tab.formattedTotal, '€8.50');
+      });
+    });
+
+    group('isOpen', () {
+      test('returns true for open status', () {
+        final tab = BarTab(
+          id: 'tab-1',
+          customerName: 'John',
+          status: 'open',
+          openedAt: DateTime.now(),
+          items: const [],
+        );
+
+        expect(tab.isOpen, true);
+      });
+
+      test('returns false for closed status', () {
+        final tab = BarTab(
+          id: 'tab-1',
+          customerName: 'John',
+          status: 'closed',
+          openedAt: DateTime.now(),
+          items: const [],
+        );
+
+        expect(tab.isOpen, false);
+      });
+    });
+  });
+}
diff --git a/test/bar_tab_service_test.dart b/test/bar_tab_service_test.dart
new file mode 100644
index 0000000..1f544fe
--- /dev/null
+++ b/test/bar_tab_service_test.dart
@@ -0,0 +1,284 @@
+import 'package:drift/drift.dart' hide isNull, isNotNull;
+import 'package:drift/native.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:kooltab2/database/app_database.dart';
+import 'package:kooltab2/models/product.dart';
+import 'package:kooltab2/services/bar_tab_service.dart';
+
+void main() {
+  late AppDatabase database;
+  late DriftBarTabService service;
+
+  setUp(() {
+    database = AppDatabase(NativeDatabase.memory());
+    service = DriftBarTabService(database: database);
+  });
+
+  tearDown(() async {
+    await database.close();
+  });
+
+  Product createTestProduct({
+    String id = 'prod-1',
+    String name = 'Test Beer',
+    int priceInCents = 400,
+  }) {
+    return Product(
+      id: id,
+      name: name,
+      category: 'Drinks',
+      stockQuantity: 100,
+      lowStockThreshold: 10,
+      priceInCents: priceInCents,
+    );
+  }
+
+  group('DriftBarTabService', () {
+    group('createTab', () {
+      test('creates tab with open status', () async {
+        final tab = await service.createTab(customerName: 'John');
+
+        expect(tab.customerName, 'John');
+        expect(tab.status, 'open');
+        expect(tab.items, isEmpty);
+      });
+
+      test('creates tab with unique id', () async {
+        final tab1 = await service.createTab(customerName: 'John');
+        final tab2 = await service.createTab(customerName: 'Jane');
+
+        expect(tab1.id, isNot(equals(tab2.id)));
+      });
+    });
+
+    group('getOpenTabs', () {
+      test('returns empty list when no tabs', () async {
+        final tabs = await service.getOpenTabs();
+        expect(tabs, isEmpty);
+      });
+
+      test('returns only open tabs', () async {
+        await service.createTab(customerName: 'Open Tab');
+        await database.into(database.barTabs).insert(
+          BarTabsCompanion.insert(
+            id: 'closed-tab',
+            customerName: 'Closed Tab',
+            status: const Value('closed'),
+            openedAt: DateTime.now(),
+          ),
+        );
+
+        final tabs = await service.getOpenTabs();
+
+        expect(tabs.length, 1);
+        expect(tabs.first.customerName, 'Open Tab');
+      });
+
+      test('tabs sorted by openedAt descending', () async {
+        final now = DateTime.now();
+        await database.into(database.barTabs).insert(
+          BarTabsCompanion.insert(
+            id: 'tab-first',
+            customerName: 'First',
+            status: const Value('open'),
+            openedAt: now.subtract(const Duration(hours: 1)),
+          ),
+        );
+        await database.into(database.barTabs).insert(
+          BarTabsCompanion.insert(
+            id: 'tab-second',
+            customerName: 'Second',
+            status: const Value('open'),
+            openedAt: now,
+          ),
+        );
+
+        final tabs = await service.getOpenTabs();
+
+        expect(tabs.first.customerName, 'Second');
+        expect(tabs.last.customerName, 'First');
+      });
+    });
+
+    group('getTabById', () {
+      test('returns tab when exists', () async {
+        final created = await service.createTab(customerName: 'Test');
+
+        final tab = await service.getTabById(created.id);
+
+        expect(tab, isNotNull);
+        expect(tab!.customerName, 'Test');
+      });
+
+      test('returns null when not exists', () async {
+        final tab = await service.getTabById('nonexistent');
+        expect(tab, isNull);
+      });
+    });
+
+    group('addProductToTab', () {
+      test('adds new product to tab', () async {
+        final tab = await service.createTab(customerName: 'John');
+        final product = createTestProduct();
+
+        await service.addProductToTab(tabId: tab.id, product: product);
+
+        final updatedTab = await service.getTabById(tab.id);
+        expect(updatedTab!.items.length, 1);
+        expect(updatedTab.items.first.productName, 'Test Beer');
+        expect(updatedTab.items.first.quantity, 1);
+      });
+
+      test('increments quantity when product already in tab', () async {
+        final tab = await service.createTab(customerName: 'John');
+        final product = createTestProduct();
+
+        await service.addProductToTab(tabId: tab.id, product: product);
+        await service.addProductToTab(tabId: tab.id, product: product);
+        await service.addProductToTab(tabId: tab.id, product: product);
+
+        final updatedTab = await service.getTabById(tab.id);
+        expect(updatedTab!.items.length, 1);
+        expect(updatedTab.items.first.quantity, 3);
+      });
+
+      test('adding product calculates correct line total', () async {
+        final tab = await service.createTab(customerName: 'John');
+        final product = createTestProduct(priceInCents: 450);
+
+        await service.addProductToTab(tabId: tab.id, product: product);
+        await service.addProductToTab(tabId: tab.id, product: product);
+
+        final updatedTab = await service.getTabById(tab.id);
+        expect(updatedTab!.items.first.lineTotalInCents, 900);
+      });
+    });
+
+    group('updateTabItemQuantity', () {
+      test('updates item quantity', () async {
+        final tab = await service.createTab(customerName: 'John');
+        final product = createTestProduct();
+        await service.addProductToTab(tabId: tab.id, product: product);
+
+        final tabItemId = (await service.getTabById(tab.id))!.items.first.id;
+
+        await service.updateTabItemQuantity(
+          tabItemId: tabItemId,
+          quantity: 5,
+        );
+
+        final updatedTab = await service.getTabById(tab.id);
+        expect(updatedTab!.items.first.quantity, 5);
+      });
+
+      test('deletes item when quantity is zero', () async {
+        final tab = await service.createTab(customerName: 'John');
+        final product = createTestProduct();
+        await service.addProductToTab(tabId: tab.id, product: product);
+
+        final tabItemId = (await service.getTabById(tab.id))!.items.first.id;
+
+        await service.updateTabItemQuantity(tabItemId: tabItemId, quantity: 0);
+
+        final updatedTab = await service.getTabById(tab.id);
+        expect(updatedTab!.items, isEmpty);
+      });
+
+      test('deletes item when quantity is negative', () async {
+        final tab = await service.createTab(customerName: 'John');
+        final product = createTestProduct();
+        await service.addProductToTab(tabId: tab.id, product: product);
+
+        final tabItemId = (await service.getTabById(tab.id))!.items.first.id;
+
+        await service.updateTabItemQuantity(tabItemId: tabItemId, quantity: -1);
+
+        final updatedTab = await service.getTabById(tab.id);
+        expect(updatedTab!.items, isEmpty);
+      });
+    });
+
+    group('closeTab', () {
+      test('archives tab items to closed tabs', () async {
+        final tab = await service.createTab(customerName: 'John');
+        final product = createTestProduct();
+        await service.addProductToTab(tabId: tab.id, product: product);
+        await service.addProductToTab(tabId: tab.id, product: product);
+
+        await service.closeTab(tab.id);
+
+        final closedTabs = await service.getClosedTabs();
+        expect(closedTabs.length, 1);
+        expect(closedTabs.first.customerName, 'John');
+        expect(closedTabs.first.items.length, 1);
+        expect(closedTabs.first.items.first.quantity, 2);
+      });
+
+      test('clears tab items after closing', () async {
+        final tab = await service.createTab(customerName: 'John');
+        final product = createTestProduct();
+        await service.addProductToTab(tabId: tab.id, product: product);
+
+        await service.closeTab(tab.id);
+
+        final updatedTab = await service.getTabById(tab.id);
+        expect(updatedTab!.items, isEmpty);
+      });
+
+      test('tab remains open but items cleared', () async {
+        final tab = await service.createTab(customerName: 'John');
+        final product = createTestProduct();
+        await service.addProductToTab(tabId: tab.id, product: product);
+
+        await service.closeTab(tab.id);
+
+        final updatedTab = await service.getTabById(tab.id);
+        expect(updatedTab!.isOpen, true);
+        expect(updatedTab.items, isEmpty);
+      });
+
+      test('closed tab preserves item prices', () async {
+        final tab = await service.createTab(customerName: 'John');
+        final product = createTestProduct(priceInCents: 550);
+        await service.addProductToTab(tabId: tab.id, product: product);
+
+        await service.closeTab(tab.id);
+
+        final closedTabs = await service.getClosedTabs();
+        expect(closedTabs.first.items.first.unitPriceInCents, 550);
+      });
+    });
+
+    group('getClosedTabs', () {
+      test('returns empty when no closed tabs', () async {
+        final tabs = await service.getClosedTabs();
+        expect(tabs, isEmpty);
+      });
+
+      test('returns closed tabs sorted by closedAt descending', () async {
+        final now = DateTime.now();
+        await database.into(database.closedTabs).insert(
+          ClosedTabsCompanion.insert(
+            id: 'closed-first',
+            originalTabId: 'original-1',
+            customerName: 'First',
+            closedAt: now.subtract(const Duration(hours: 1)),
+          ),
+        );
+        await database.into(database.closedTabs).insert(
+          ClosedTabsCompanion.insert(
+            id: 'closed-second',
+            originalTabId: 'original-2',
+            customerName: 'Second',
+            closedAt: now,
+          ),
+        );
+
+        final closedTabs = await service.getClosedTabs();
+
+        expect(closedTabs.first.customerName, 'Second');
+        expect(closedTabs.last.customerName, 'First');
+      });
+    });
+  });
+}
diff --git a/test/inventory_view_model_test.dart b/test/inventory_view_model_test.dart
new file mode 100644
index 0000000..ef6773a
--- /dev/null
+++ b/test/inventory_view_model_test.dart
@@ -0,0 +1,157 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:mocktail/mocktail.dart';
+import 'package:kooltab2/models/product.dart';
+import 'package:kooltab2/services/product_service.dart';
+import 'package:kooltab2/viewmodels/inventory_view_model.dart';
+
+class MockProductService extends Mock implements ProductService {}
+
+void main() {
+  late InventoryViewModel viewModel;
+  late MockProductService mockService;
+
+  setUp(() {
+    mockService = MockProductService();
+    viewModel = InventoryViewModel(productService: mockService);
+  });
+
+  setUpAll(() {
+    registerFallbackValue(const Product(
+      id: 'fallback',
+      name: 'Fallback',
+      category: 'Test',
+      stockQuantity: 0,
+      lowStockThreshold: 0,
+      priceInCents: 0,
+    ));
+  });
+
+  final testProducts = [
+    const Product(
+      id: 'prod-1',
+      name: 'Beer',
+      category: 'Drinks',
+      stockQuantity: 20,
+      lowStockThreshold: 5,
+      priceInCents: 400,
+    ),
+    const Product(
+      id: 'prod-2',
+      name: 'Wine',
+      category: 'Drinks',
+      stockQuantity: 3,
+      lowStockThreshold: 5,
+      priceInCents: 600,
+    ),
+  ];
+
+  group('InventoryViewModel', () {
+    group('load', () {
+      test('loads products from service', () async {
+        when(() => mockService.getProducts())
+            .thenAnswer((_) async => testProducts);
+
+        await viewModel.load();
+
+        expect(viewModel.products, testProducts);
+        verify(() => mockService.getProducts()).called(1);
+      });
+
+      test('notifies listeners after load', () async {
+        var notifyCount = 0;
+        viewModel.addListener(() => notifyCount++);
+        when(() => mockService.getProducts())
+            .thenAnswer((_) async => testProducts);
+
+        await viewModel.load();
+
+        expect(notifyCount, 1);
+      });
+    });
+
+    group('decreaseStock', () {
+      test('decreases stock via service', () async {
+        when(() => mockService.decreaseStock('prod-1', 3))
+            .thenAnswer((_) async {});
+
+        await viewModel.decreaseStock('prod-1', 3);
+
+        verify(() => mockService.decreaseStock('prod-1', 3)).called(1);
+      });
+
+      test('updates local product cache', () async {
+        when(() => mockService.getProducts())
+            .thenAnswer((_) async => testProducts);
+        when(() => mockService.decreaseStock('prod-1', 5))
+            .thenAnswer((_) async {});
+
+        await viewModel.load();
+        await viewModel.decreaseStock('prod-1', 5);
+
+        final product = viewModel.products.firstWhere((p) => p.id == 'prod-1');
+        expect(product.stockQuantity, 15);
+      });
+
+      test('notifies listeners after decrease', () async {
+        var notifyCount = 0;
+        viewModel.addListener(() => notifyCount++);
+        when(() => mockService.decreaseStock('prod-1', 1))
+            .thenAnswer((_) async {});
+
+        await viewModel.decreaseStock('prod-1', 1);
+
+        expect(notifyCount, 1);
+      });
+    });
+
+    group('increaseStock', () {
+      test('increases stock via service', () async {
+        when(() => mockService.increaseStock('prod-1', 5))
+            .thenAnswer((_) async {});
+
+        await viewModel.increaseStock('prod-1', 5);
+
+        verify(() => mockService.increaseStock('prod-1', 5)).called(1);
+      });
+
+      test('updates local product cache', () async {
+        when(() => mockService.getProducts())
+            .thenAnswer((_) async => testProducts);
+        when(() => mockService.increaseStock('prod-2', 2))
+            .thenAnswer((_) async {});
+
+        await viewModel.load();
+        await viewModel.increaseStock('prod-2', 2);
+
+        final product = viewModel.products.firstWhere((p) => p.id == 'prod-2');
+        expect(product.stockQuantity, 5);
+      });
+
+      test('notifies listeners after increase', () async {
+        var notifyCount = 0;
+        viewModel.addListener(() => notifyCount++);
+        when(() => mockService.increaseStock('prod-1', 1))
+            .thenAnswer((_) async {});
+
+        await viewModel.increaseStock('prod-1', 1);
+
+        expect(notifyCount, 1);
+      });
+    });
+
+    group('edge cases', () {
+      test('handles decrease for product not in local cache', () async {
+        when(() => mockService.getProducts())
+            .thenAnswer((_) async => testProducts);
+        when(() => mockService.decreaseStock('unknown', 1))
+            .thenAnswer((_) async {});
+
+        await viewModel.load();
+        await viewModel.decreaseStock('unknown', 1);
+
+        verify(() => mockService.decreaseStock('unknown', 1)).called(1);
+        expect(viewModel.products.length, 2);
+      });
+    });
+  });
+}
diff --git a/test/pin_lock_service_test.dart b/test/pin_lock_service_test.dart
new file mode 100644
index 0000000..d891264
--- /dev/null
+++ b/test/pin_lock_service_test.dart
@@ -0,0 +1,150 @@
+import 'dart:convert';
+
+import 'package:crypto/crypto.dart';
+import 'package:flutter_secure_storage/flutter_secure_storage.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:mocktail/mocktail.dart';
+import 'package:kooltab2/services/pin_lock_service.dart';
+
+class MockFlutterSecureStorage extends Mock
+    implements FlutterSecureStorage {}
+
+String _computeHash(String pin, String salt) {
+  final bytes = utf8.encode('$salt:$pin');
+  return sha256.convert(bytes).toString();
+}
+
+void main() {
+  late PinLockService service;
+  late MockFlutterSecureStorage mockStorage;
+
+  setUp(() {
+    mockStorage = MockFlutterSecureStorage();
+    service = PinLockService(storage: mockStorage);
+  });
+
+  group('PinLockService', () {
+    group('hasPin', () {
+      test('returns false when no hash stored', () async {
+        when(() => mockStorage.read(key: 'pin_hash'))
+            .thenAnswer((_) async => null);
+
+        final result = await service.hasPin();
+
+        expect(result, false);
+      });
+
+      test('returns false when hash is empty', () async {
+        when(() => mockStorage.read(key: 'pin_hash'))
+            .thenAnswer((_) async => '');
+
+        final result = await service.hasPin();
+
+        expect(result, false);
+      });
+
+      test('returns true when hash exists', () async {
+        when(() => mockStorage.read(key: 'pin_hash'))
+            .thenAnswer((_) async => 'somehash');
+
+        final result = await service.hasPin();
+
+        expect(result, true);
+      });
+    });
+
+    group('setPin', () {
+      test('stores salt and hash', () async {
+        when(() => mockStorage.write(key: any(named: 'key'), value: any(named: 'value')))
+            .thenAnswer((_) async {});
+
+        await service.setPin('1234');
+
+        verify(() => mockStorage.write(key: 'pin_salt', value: any(named: 'value'))).called(1);
+        verify(() => mockStorage.write(key: 'pin_hash', value: any(named: 'value'))).called(1);
+      });
+
+      test('generates unique salts for different pins', () async {
+        when(() => mockStorage.write(key: any(named: 'key'), value: any(named: 'value')))
+            .thenAnswer((_) async {});
+
+        await service.setPin('1234');
+        final firstSaltCapture = verify(() => mockStorage.write(
+          key: 'pin_salt',
+          value: captureAny(named: 'value'),
+        )).captured.first;
+
+        await service.setPin('5678');
+        final secondSaltCapture = verify(() => mockStorage.write(
+          key: 'pin_salt',
+          value: captureAny(named: 'value'),
+        )).captured.last;
+
+        expect(firstSaltCapture, isNot(equals(secondSaltCapture)));
+      });
+    });
+
+    group('verifyPin', () {
+      test('returns false when salt is missing', () async {
+        when(() => mockStorage.read(key: 'pin_salt'))
+            .thenAnswer((_) async => null);
+        when(() => mockStorage.read(key: 'pin_hash'))
+            .thenAnswer((_) async => 'somehash');
+
+        final result = await service.verifyPin('1234');
+
+        expect(result, false);
+      });
+
+      test('returns false when hash is missing', () async {
+        when(() => mockStorage.read(key: 'pin_salt'))
+            .thenAnswer((_) async => 'somesalt');
+        when(() => mockStorage.read(key: 'pin_hash'))
+            .thenAnswer((_) async => null);
+
+        final result = await service.verifyPin('1234');
+
+        expect(result, false);
+      });
+
+      test('returns true for correct pin', () async {
+        const salt = 'test_salt';
+        const pin = '1234';
+        final expectedHash = _computeHash(pin, salt);
+        when(() => mockStorage.read(key: 'pin_salt'))
+            .thenAnswer((_) async => salt);
+        when(() => mockStorage.read(key: 'pin_hash'))
+            .thenAnswer((_) async => expectedHash);
+
+        final result = await service.verifyPin('1234');
+
+        expect(result, true);
+      });
+
+      test('returns false for incorrect pin', () async {
+        const salt = 'test_salt';
+        final correctHash = _computeHash('1234', salt);
+        when(() => mockStorage.read(key: 'pin_salt'))
+            .thenAnswer((_) async => salt);
+        when(() => mockStorage.read(key: 'pin_hash'))
+            .thenAnswer((_) async => correctHash);
+
+        final result = await service.verifyPin('5678');
+
+        expect(result, false);
+      });
+    });
+
+    group('clearPin', () {
+      test('deletes both salt and hash', () async {
+        when(() => mockStorage.delete(key: any(named: 'key')))
+            .thenAnswer((_) async {});
+
+        await service.clearPin();
+
+        verify(() => mockStorage.delete(key: 'pin_salt')).called(1);
+        verify(() => mockStorage.delete(key: 'pin_hash')).called(1);
+      });
+    });
+  });
+}
diff --git a/test/product_model_test.dart b/test/product_model_test.dart
new file mode 100644
index 0000000..4031afc
--- /dev/null
+++ b/test/product_model_test.dart
@@ -0,0 +1,132 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:kooltab2/models/product.dart';
+
+void main() {
+  group('Product', () {
+    group('isLowStock', () {
+      test('returns true when stock equals threshold', () {
+        const product = Product(
+          id: '1',
+          name: 'Test',
+          category: 'Drinks',
+          stockQuantity: 5,
+          lowStockThreshold: 5,
+          priceInCents: 100,
+        );
+
+        expect(product.isLowStock, true);
+      });
+
+      test('returns true when stock is below threshold', () {
+        const product = Product(
+          id: '1',
+          name: 'Test',
+          category: 'Drinks',
+          stockQuantity: 3,
+          lowStockThreshold: 5,
+          priceInCents: 100,
+        );
+
+        expect(product.isLowStock, true);
+      });
+
+      test('returns false when stock is above threshold', () {
+        const product = Product(
+          id: '1',
+          name: 'Test',
+          category: 'Drinks',
+          stockQuantity: 10,
+          lowStockThreshold: 5,
+          priceInCents: 100,
+        );
+
+        expect(product.isLowStock, false);
+      });
+    });
+
+    group('formattedPrice', () {
+      test('formats price with euro symbol and 2 decimals', () {
+        const product = Product(
+          id: '1',
+          name: 'Test',
+          category: 'Drinks',
+          stockQuantity: 10,
+          lowStockThreshold: 5,
+          priceInCents: 1234,
+        );
+
+        expect(product.formattedPrice, '€12.34');
+      });
+
+      test('formats zero price correctly', () {
+        const product = Product(
+          id: '1',
+          name: 'Test',
+          category: 'Drinks',
+          stockQuantity: 10,
+          lowStockThreshold: 5,
+          priceInCents: 0,
+        );
+
+        expect(product.formattedPrice, '€0.00');
+      });
+
+      test('formats whole euros correctly', () {
+        const product = Product(
+          id: '1',
+          name: 'Test',
+          category: 'Drinks',
+          stockQuantity: 10,
+          lowStockThreshold: 5,
+          priceInCents: 500,
+        );
+
+        expect(product.formattedPrice, '€5.00');
+      });
+    });
+
+    group('copyWith', () {
+      test('creates copy with updated fields', () {
+        const original = Product(
+          id: '1',
+          name: 'Original',
+          category: 'Drinks',
+          stockQuantity: 10,
+          lowStockThreshold: 5,
+          priceInCents: 100,
+        );
+
+        final copy = original.copyWith(name: 'Updated', stockQuantity: 20);
+
+        expect(copy.name, 'Updated');
+        expect(copy.stockQuantity, 20);
+        expect(copy.id, '1');
+        expect(copy.category, 'Drinks');
+      });
+
+      test('preserves original values when not specified', () {
+        const original = Product(
+          id: '1',
+          name: 'Test',
+          category: 'Food',
+          stockQuantity: 15,
+          lowStockThreshold: 3,
+          priceInCents: 750,
+          imagePath: '/path/to/image.jpg',
+          active: false,
+        );
+
+        final copy = original.copyWith();
+
+        expect(copy.id, '1');
+        expect(copy.name, 'Test');
+        expect(copy.category, 'Food');
+        expect(copy.stockQuantity, 15);
+        expect(copy.lowStockThreshold, 3);
+        expect(copy.priceInCents, 750);
+        expect(copy.imagePath, '/path/to/image.jpg');
+        expect(copy.active, false);
+      });
+    });
+  });
+}
diff --git a/test/product_service_test.dart b/test/product_service_test.dart
new file mode 100644
index 0000000..ec2637a
--- /dev/null
+++ b/test/product_service_test.dart
@@ -0,0 +1,253 @@
+import 'package:drift/drift.dart' hide isNull, isNotNull;
+import 'package:drift/native.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:kooltab2/database/app_database.dart';
+import 'package:kooltab2/models/product.dart';
+import 'package:kooltab2/services/product_service.dart';
+
+void main() {
+  late AppDatabase database;
+  late DriftProductService service;
+
+  setUp(() {
+    database = AppDatabase(NativeDatabase.memory());
+    service = DriftProductService(database: database);
+  });
+
+  tearDown(() async {
+    await database.close();
+  });
+
+  group('DriftProductService', () {
+    group('getProducts', () {
+      test('returns empty list when no products', () async {
+        final products = await service.getProducts();
+        expect(products, isEmpty);
+      });
+
+      test('returns only active products', () async {
+        await database.into(database.products).insert(
+          ProductsCompanion.insert(
+            id: '1',
+            name: 'Active Product',
+            category: 'Drinks',
+            stockQuantity: 10,
+            lowStockThreshold: 2,
+            priceInCents: 500,
+          ),
+        );
+        await database.into(database.products).insert(
+          ProductsCompanion.insert(
+            id: '2',
+            name: 'Inactive Product',
+            category: 'Drinks',
+            stockQuantity: 5,
+            lowStockThreshold: 1,
+            priceInCents: 300,
+            active: const Value(false),
+          ),
+        );
+
+        final products = await service.getProducts();
+
+        expect(products.length, 1);
+        expect(products.first.name, 'Active Product');
+      });
+
+      test('returns products sorted by name', () async {
+        await database.into(database.products).insert(
+          ProductsCompanion.insert(
+            id: '1',
+            name: 'Zebra',
+            category: 'Drinks',
+            stockQuantity: 10,
+            lowStockThreshold: 2,
+            priceInCents: 500,
+          ),
+        );
+        await database.into(database.products).insert(
+          ProductsCompanion.insert(
+            id: '2',
+            name: 'Apple',
+            category: 'Drinks',
+            stockQuantity: 5,
+            lowStockThreshold: 1,
+            priceInCents: 300,
+          ),
+        );
+
+        final products = await service.getProducts();
+
+        expect(products.first.name, 'Apple');
+        expect(products.last.name, 'Zebra');
+      });
+    });
+
+    group('getProductById', () {
+      test('returns product when exists', () async {
+        await database.into(database.products).insert(
+          ProductsCompanion.insert(
+            id: 'prod-123',
+            name: 'Test Product',
+            category: 'Drinks',
+            stockQuantity: 10,
+            lowStockThreshold: 2,
+            priceInCents: 500,
+          ),
+        );
+
+        final product = await service.getProductById('prod-123');
+
+        expect(product, isNotNull);
+        expect(product!.name, 'Test Product');
+      });
+
+      test('returns null when not exists', () async {
+        final product = await service.getProductById('nonexistent');
+        expect(product, isNull);
+      });
+    });
+
+    group('createProduct', () {
+      test('creates product successfully', () async {
+        await service.createProduct(
+          name: 'New Product',
+          category: 'Food',
+          stockQuantity: 20,
+          lowStockThreshold: 5,
+          priceInCents: 850,
+          imagePath: null,
+        );
+
+        final products = await service.getProducts();
+        expect(products.length, 1);
+        expect(products.first.name, 'New Product');
+        expect(products.first.stockQuantity, 20);
+      });
+    });
+
+    group('updateProduct', () {
+      test('updates product fields', () async {
+        await database.into(database.products).insert(
+          ProductsCompanion.insert(
+            id: 'update-test',
+            name: 'Original',
+            category: 'Drinks',
+            stockQuantity: 10,
+            lowStockThreshold: 2,
+            priceInCents: 500,
+          ),
+        );
+
+        await service.updateProduct(
+          const Product(
+            id: 'update-test',
+            name: 'Updated',
+            category: 'Food',
+            stockQuantity: 15,
+            lowStockThreshold: 3,
+            priceInCents: 750,
+            active: true,
+          ),
+        );
+
+        final product = await service.getProductById('update-test');
+        expect(product!.name, 'Updated');
+        expect(product.stockQuantity, 15);
+        expect(product.priceInCents, 750);
+      });
+    });
+
+    group('deleteProduct', () {
+      test('removes product from database', () async {
+        await database.into(database.products).insert(
+          ProductsCompanion.insert(
+            id: 'delete-test',
+            name: 'To Delete',
+            category: 'Drinks',
+            stockQuantity: 10,
+            lowStockThreshold: 2,
+            priceInCents: 500,
+          ),
+        );
+
+        await service.deleteProduct('delete-test');
+
+        final products = await database.select(database.products).get();
+        expect(products, isEmpty);
+      });
+    });
+
+    group('decreaseStock', () {
+      test('decreases stock quantity', () async {
+        await database.into(database.products).insert(
+          ProductsCompanion.insert(
+            id: 'stock-test',
+            name: 'Stock Test',
+            category: 'Drinks',
+            stockQuantity: 10,
+            lowStockThreshold: 2,
+            priceInCents: 500,
+          ),
+        );
+
+        await service.decreaseStock('stock-test', 3);
+
+        final product = await service.getProductById('stock-test');
+        expect(product!.stockQuantity, 7);
+      });
+
+      test('throws when product not found', () async {
+        expect(
+          () => service.decreaseStock('nonexistent', 1),
+          throwsA(isA<Exception>()),
+        );
+      });
+
+      test('throws when not enough stock', () async {
+        await database.into(database.products).insert(
+          ProductsCompanion.insert(
+            id: 'low-stock',
+            name: 'Low Stock',
+            category: 'Drinks',
+            stockQuantity: 3,
+            lowStockThreshold: 1,
+            priceInCents: 500,
+          ),
+        );
+
+        expect(
+          () => service.decreaseStock('low-stock', 5),
+          throwsA(isA<Exception>()),
+        );
+      });
+    });
+
+    group('increaseStock', () {
+      test('increases stock quantity', () async {
+        await database.into(database.products).insert(
+          ProductsCompanion.insert(
+            id: 'increase-test',
+            name: 'Increase Test',
+            category: 'Drinks',
+            stockQuantity: 10,
+            lowStockThreshold: 2,
+            priceInCents: 500,
+          ),
+        );
+
+        await service.increaseStock('increase-test', 5);
+
+        final product = await service.getProductById('increase-test');
+        expect(product!.stockQuantity, 15);
+      });
+
+      test('throws when product not found', () async {
+        expect(
+          () => service.increaseStock('nonexistent', 1),
+          throwsA(isA<Exception>()),
+        );
+      });
+    });
+  });
+}