public void Shopping_Cart_Add_New_Item()
{
//Arrange
var mockStrategy = new Mock <IDeliveryStrategy>();
var context = new ShoppingCartContext(mockStrategy.Object);
var expectedCount = 1;
//Act
context.AddItem(new Product("tv", new Category("electronics"), 30, 1));
//Assert
Assert.Equal(expectedCount, context.GetItemCount());
}