nearle_pos/test/unit/checkout_test.dart

import 'package:flutter_test/flutter_test.dart';
import 'package:nearle_pos/data/datasources/local_store.dart';
import 'package:nearle_pos/data/repositories/customer_repository_impl.dart';
import 'package:nearle_pos/data/repositories/product_repository_impl.dart';
import 'package:nearle_pos/data/repositories/transaction_repository_impl.dart';
import 'package:nearle_pos/domain/entities/cart.dart';
import 'package:nearle_pos/domain/entities/customer.dart';
import 'package:nearle_pos/domain/entities/transaction.dart';
import 'package:nearle_pos/domain/usecases/checkout_sale.dart';

void main() {
  late LocalStore store;
  late ProductRepositoryImpl products;
  late CustomerRepositoryImpl customers;
  late TransactionRepositoryImpl transactions;
  late CheckoutSale checkout;

  setUp(() async {
    store = LocalStore.instance;
    // Fresh seed for every test so stock and invoice sequence never leak.
    await store.reset();

    products = ProductRepositoryImpl(store);
    customers = CustomerRepositoryImpl(store);
    transactions = TransactionRepositoryImpl(store);
    checkout = CheckoutSale(
      productRepository: products,
      customerRepository: customers,
      transactionRepository: transactions,
    );
  });

  /// Amul Milk 1L: 62.00, 5% GST, 50 in stock.
  Future<Cart> milkCart({int qty = 2, String? customerId}) async {
    final milk = (await products.findByBarcode('8901234500011'))!;
    final customer =
        customerId == null ? null : await customers.findById(customerId);
    return Cart(
      lines: [CartLine(product: milk, quantity: qty.toDouble())],
      customer: customer,
    );
  }

  group('successful checkout', () {
    test('records the sale and returns an invoice', () async {
      final cart = await milkCart();
      expect(cart.grandTotal, 124);

      final result = await checkout(
        cart: cart,
        payments: const [
          PaymentSplit(method: PaymentMethod.cash, amount: 124, tendered: 200),
        ],
        cashierName: 'Suriya',
      );

      final txn = result.transaction;
      expect(txn.total, 124);
      expect(txn.amountPaid, 124);
      expect(txn.changeDue, 76);
      expect(txn.isFullySettled, isTrue);
      expect(txn.isSplit, isFalse);
      expect(txn.invoiceNumber, contains('00001'));
      expect(txn.status, TransactionStatus.completed);
    });

    test('decrements stock by the quantity sold', () async {
      final cart = await milkCart();

      await checkout(
        cart: cart,
        payments: const [
          PaymentSplit(method: PaymentMethod.cash, amount: 124, tendered: 124),
        ],
        cashierName: 'Suriya',
      );

      final milk = await products.findByBarcode('8901234500011');
      expect(milk!.stock, 48);
    });

    test('persists the transaction to history', () async {
      final cart = await milkCart();

      await checkout(
        cart: cart,
        payments: const [
          PaymentSplit(method: PaymentMethod.cash, amount: 124, tendered: 124),
        ],
        cashierName: 'Suriya',
      );

      final history = await transactions.history();
      expect(history, hasLength(1));
      expect(await transactions.salesTotalForDay(DateTime.now()), 124);
    });

    test('accepts a split across two tenders', () async {
      final cart = await milkCart();

      final result = await checkout(
        cart: cart,
        payments: const [
          PaymentSplit(method: PaymentMethod.cash, amount: 100, tendered: 100),
          PaymentSplit(
            method: PaymentMethod.upi,
            amount: 24,
            reference: 'UPI-991',
          ),
        ],
        cashierName: 'Suriya',
      );

      expect(result.transaction.isSplit, isTrue);
      expect(result.transaction.amountPaid, 124);
      expect(result.transaction.paymentSummary, 'Cash + UPI');
    });

    test('moves loyalty points and lifetime spend for a member', () async {
      final cart = await milkCart(customerId: 'c001');

      // 124 less the 2% silver discount, rounded.
      expect(cart.membershipDiscountAmount, 2.48);
      expect(cart.grandTotal, 122);
      expect(cart.pointsEarned, 12);

      final result = await checkout(
        cart: cart,
        payments: const [
          PaymentSplit(method: PaymentMethod.cash, amount: 122, tendered: 200),
        ],
        cashierName: 'Suriya',
      );

      final updated = result.updatedCustomer!;
      expect(updated.loyaltyPoints, 332); // 320 + 12
      expect(updated.lifetimeSpend, 24622); // 24500 + 122
      expect(updated.visitCount, 42);
    });
  });

  group('rejected checkout', () {
    test('refuses an empty cart', () async {
      expect(
        () => checkout(
          cart: Cart.empty,
          payments: const [
            PaymentSplit(method: PaymentMethod.cash, amount: 0),
          ],
          cashierName: 'Suriya',
        ),
        throwsA(isA<CheckoutFailure>()),
      );
    });

    test('refuses a bill with no tender', () async {
      final cart = await milkCart();
      expect(
        () => checkout(cart: cart, payments: const [], cashierName: 'Suriya'),
        throwsA(isA<CheckoutFailure>()),
      );
    });

    test('refuses an underpayment', () async {
      final cart = await milkCart();
      expect(
        () => checkout(
          cart: cart,
          payments: const [
            PaymentSplit(method: PaymentMethod.cash, amount: 100, tendered: 100),
          ],
          cashierName: 'Suriya',
        ),
        throwsA(isA<CheckoutFailure>()),
      );
    });

    test('refuses to sell more than is in stock', () async {
      final cart = await milkCart(qty: 999);
      expect(
        () => checkout(
          cart: cart,
          payments: [
            PaymentSplit(
              method: PaymentMethod.cash,
              amount: cart.grandTotal,
              tendered: cart.grandTotal,
            ),
          ],
          cashierName: 'Suriya',
        ),
        throwsA(isA<CheckoutFailure>()),
      );
    });

    test('leaves stock untouched when validation fails', () async {
      final cart = await milkCart();
      try {
        await checkout(cart: cart, payments: const [], cashierName: 'Suriya');
      } on CheckoutFailure {
        // expected
      }

      final milk = await products.findByBarcode('8901234500011');
      expect(milk!.stock, 50);
    });
  });

  group('repositories', () {
    test('finds a customer by mobile number', () async {
      final found = await customers.findByMobile('9876543210');
      expect(found?.name, 'Abhishek');
      expect(await customers.findByMobile('0000000000'), isNull);
    });

    test('rejects a duplicate mobile number on create', () async {
      // 9876543210 already belongs to the seeded customer c001.
      expect(
        () => customers.create(
          const Customer(id: '', name: 'Impostor', mobile: '9876543210'),
        ),
        throwsA(isA<StateError>()),
      );
    });

    test('creates a customer with a generated id and zeroed loyalty', () async {
      final created = await customers.create(
        const Customer(id: '', name: 'New Shopper', mobile: '9000011111'),
      );

      expect(created.id, isNotEmpty);
      expect(created.loyaltyPoints, 0);
      expect(created.lifetimeSpend, 0);
      expect(created.tier, MembershipTier.bronze);
      expect(await customers.findByMobile('9000011111'), isNotNull);
    });

    test('ranks an exact barcode above a fuzzy name match', () async {
      final results = await products.search('8901234500011');
      expect(results.first.name, 'Amul Milk 1L');
    });

    test('parks and resumes a bill', () async {
      final cart = await milkCart();
      await transactions.park(
        ParkedBill(id: 'park-1', cart: cart, parkedAt: DateTime.now()),
      );

      expect(await transactions.parkedBills(), hasLength(1));
      await transactions.removeParked('park-1');
      expect(await transactions.parkedBills(), isEmpty);
    });
  });
}