public void ShouldGetTheThirdFreeAndNotFreeShipping()
        {
            // ARRANGE
            var productA = new Product {Price = 1.28m, Name = "Widget"};
            var productB = new Product {Price = 2.56m, Name = "Do Hickey"};

            var cart = new ShoppingCart
            {
                Products = new List<Product> {productA, productB, productA, productB, productA}
            };

            var sut = new RulesEngineImpleamentation(cart);

            // ACT
            ShoppingCart result = sut.Run();

            // ASSERT
            const decimal expectedTotal = 7.68m;
            result.FreeShippng.Should().BeFalse();
            result.TotalValue.Should().Be(expectedTotal);
        }
 public RulesEngineImpleamentation(ShoppingCart shoppingCart)
 {
     _shoppingCart = shoppingCart;
 }