public void SubTotal_2ItemsOfPrice10_Returns20()
{
var product1 = new Product("SKU");
product1.Price = 10;
cart.AddItem(product1, 1);
var product2 = new Product("SKU2");
product2.Price = 10;
cart.AddItem(product2, 1);
Assert.AreEqual(20, cart.SubTotal);
}