public void ShouldRemoveImmutably()
{
//Arrange
Toppings initial = new Toppings();
IToppings multiple = initial.Add(Topping.Mushroom).Add(Topping.Mozzarella);
//Act
IToppings removed = multiple.Remove(Topping.Mushroom);
//Assert
removed.Cost(new Money(10)).Should().Be(new Money(1));
multiple.Cost(new Money(10)).Should().Be(new Money(2));
}
public Money Price() => _basePrice + _toppings.Cost(_basePrice);
