左右互搏術：ChatGPT 與 TDD 結合心得

// ShoppingCart.test.ts

import { ShoppingCart, Item } from "./ShoppingCart";
import DiscountManager from "./DiscountManager"; // Import DiscountManager

describe('ShoppingCart', () => {
    let cart: ShoppingCart;
    let itemA: Item;
    let itemB: Item;
    let discountManager: DiscountManager; // Add DiscountManager

    beforeEach(() => {
        discountManager = new DiscountManager();
        cart = new ShoppingCart(discountManager);
        itemA = new Item(1, 'Product A', 10);
        itemB = new Item(2, 'Product B', 5);

    });

    it('should add an item to the cart', () => {
        cart.addItem(itemA, 2);
        expect(cart.getTotalItems()).toBe(2);
    });

    it('should remove an item from the cart', () => {
        cart.addItem(itemA, 2);
        cart.removeItem(itemA.id);
        expect(cart.getTotalItems()).toBe(0);
    });

    it('should update the quantity of an item in the cart', () => {
        cart.addItem(itemA, 2);
        cart.updateItemQuantity(itemA.id, 3);
        expect(cart.getItemQuantity(itemA.id)).toBe(3);
    });

    it('should calculate the total price of items in the cart', () => {
        cart.addItem(itemA, 2);
        cart.addItem(itemB, 3);
        // (10 * 2) + (5 * 3) = 20 + 15 = 35
        expect(cart.getTotalPrice()).toBe(35);
    });

    it('should calculate the total price of items in the cart', () => {
        cart.addItem(itemA, 2);
        // (10 * 2) * 2
        expect(cart.getTotalPrice()).toBe(40);
    });

    it('should clear the cart', () => {
        cart.addItem(itemA, 2);
        cart.clearCart();
        expect(cart.getTotalItems()).toBe(0);
    });

    it('should handle getting quantity for an item not in the cart', () => {
        expect(cart.getItemQuantity(itemA.id)).toBe(0);
    });

    it('should handle removing an item not in the cart', () => {
        // Removing an item that's not in the cart should not throw an error
        expect(() => cart.removeItem(itemB.id)).not.toThrow();
    });

    it('should handle updating quantity for an item not in the cart', () => {
        // Updating the quantity of an item that's not in the cart should not throw an error
        expect(() => cart.updateItemQuantity(itemB.id, 3)).not.toThrow();
    });
});

// ShoppingCart.ts

import DiscountManager from "./DiscountManager";
import Item from "./Item";

class ShoppingCart {
    private cart: { item: Item; quantity: number }[] = [];
    private discountManager: DiscountManager; // Add a DiscountManager property

    constructor(discountManager: DiscountManager) {
        this.discountManager = discountManager;
    }
    addItem(item: Item, quantity: number) {
        if (quantity <= 0) {
            return; // Do nothing for non-positive quantities
        }

        const existingItem = this.cart.find(cartItem => cartItem.item.id === item.id);

        if (existingItem) {
            existingItem.quantity += quantity;
        } else {
            this.cart.push({ item, quantity });
        }
    }

    removeItem(itemId: number) {
        const itemIndex = this.cart.findIndex(cartItem => cartItem.item.id === itemId);

        if (itemIndex !== -1) {
            this.cart.splice(itemIndex, 1);
        }
    }

    updateItemQuantity(itemId: number, quantity: number) {
        const existingItem = this.cart.find(cartItem => cartItem.item.id === itemId);

        if (existingItem) {
            existingItem.quantity = quantity;
        }
    }

    getTotalItems(): number {
        return this.cart.reduce((total, cartItem) => total + cartItem.quantity, 0);
    }

    getItemQuantity(itemId: number): number {
        const cartItem = this.cart.find(cartItem => cartItem.item.id === itemId);
        return cartItem ? cartItem.quantity : 0;
    }

    getTotalPrice(promoCode?: string): number {
        return this.cart.reduce((total, cartItem) => {
            const { item, quantity } = cartItem;
            const discountPercentage = promoCode ? this.discountManager.getDiscount(promoCode) : 0;
            const discountedPrice = item.price * (1 - discountPercentage / 100); // Apply promo code discount
            return total + discountedPrice * quantity;
        }, 0);
    }

    clearCart() {
        this.cart = [];
    }
}

export { ShoppingCart, Item };