Add Shop test

src/test/java/ShopTest.java

@@ -0,0 +1,97 @@
+import org.example.Constants;
+import org.example.Order;
+import org.example.Product;
+import org.example.Shop;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.util.HashMap;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class ShopTest {
+
+    private Shop shop;
+    private Product productA;
+    private Product productB;
+
+    @BeforeEach
+    void setUp() {
+        productA = new Product(1, "Product 1", 0.5f, 50f, Constants.lowVat);
+        productB = new Product(2, "Product 2", 1.0f, 500f, Constants.highVat);
+
+        HashMap<Product, Integer> stock = new HashMap<>();
+        stock.put(productA, 2);
+        stock.put(productB, 5);
+
+        shop = new Shop(stock);
+    }
+
+    @Test
+    void addProductToCart() {
+        shop.addProductToCart(productA);
+        shop.addProductToCart(productA);
+        shop.addProductToCart(productA); // exceeds stock
+
+        assertEquals(2, shop.getCart().get(productA));
+    }
+
+    @Test
+    void removeProductFromCart() {
+        shop.addProductToCart(productA);
+        shop.addProductToCart(productA);
+
+        shop.removeProductFromCart(productA);
+
+        assertEquals(1, shop.getCart().get(productA));
+    }
+
+    @Test
+    void setProductQuantityInCart() {
+        shop.setProductQuantityInCart(productA, 2);
+        shop.setProductQuantityInCart(productA, 5);
+
+        assertEquals(2, shop.getCart().get(productA));
+    }
+
+    @Test
+    void getStock() {
+        assertEquals(2, shop.getStock(productA));
+        assertEquals(5, shop.getStock(productB));
+    }
+
+    @Test
+    void getProductById() {
+        Product result = shop.getProductById(1);
+
+        assertNotNull(result);
+        assertEquals(productA, result);
+    }
+
+    @Test
+    void getProductByIdNotFound() {
+        assertNull(shop.getProductById(999));
+    }
+
+    @Test
+    void getProductList() {
+        List<Product> products = shop.getProductList();
+
+        assertEquals(2, products.size());
+        assertTrue(products.contains(productA));
+        assertTrue(products.contains(productB));
+    }
+
+    @Test
+    void checkout() {
+        shop.addProductToCart(productA);
+        shop.addProductToCart(productB);
+        shop.addProductToCart(productB);
+
+        Order order = shop.checkout();
+
+        assertNotNull(order);
+        assertTrue(shop.getCart().isEmpty());
+    }
+}