Add ShoppingCart test

src/test/java/ShoppingCartTest.java

@@ -0,0 +1,72 @@
+import org.example.Constants;
+import org.example.Product;
+import org.example.ShoppingCart;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class ShoppingCartTest {
+
+    private ShoppingCart cart;
+    private Product product1;
+    private Product product2;
+
+    @BeforeEach
+    void setUp() {
+        cart = new ShoppingCart();
+        product1 = new Product(1, "Produkt 1", 0.5f, 50f, Constants.lowVat);
+        product2 = new Product(2, "Produkt 2", 1.0f, 500f, Constants.highVat);
+    }
+
+    @Test
+    void addProduct() {
+        cart.addProduct(product1);
+        cart.addProduct(product1);
+
+        assertEquals(2, cart.getProductQuantity(product1));
+    }
+
+    @Test
+    void removeProduct() {
+        cart.addProduct(product1);
+        cart.addProduct(product1);
+
+        cart.removeProduct(product1);
+
+        assertEquals(1, cart.getProductQuantity(product1));
+    }
+
+    @Test
+    void removeProductZero() {
+        cart.removeProduct(product1);
+
+        assertEquals(0, cart.getProductQuantity(product1));
+    }
+
+    @Test
+    void setProductQuantityTo() {
+        cart.setProductQuantity(product1, 5);
+
+        assertEquals(5, cart.getProductQuantity(product1));
+    }
+
+    @Test
+    void setProductQuantityToZeroToRemove() {
+        cart.setProductQuantity(product1, 3);
+        cart.setProductQuantity(product1, 0);
+
+        assertEquals(0, cart.getProductQuantity(product1));
+    }
+
+    @Test
+    void clearProducts() {
+        cart.addProduct(product1);
+        cart.addProduct(product2);
+
+        cart.clearProducts();
+
+        assertEquals(0, cart.getProductQuantity(product1));
+        assertEquals(0, cart.getProductQuantity(product2));
+    }
+}