PlaceOrderPage.cs

public partial class PlaceOrderPage : BasePage
{
    private readonly PurchaseTestInput purchaseTestInput;
    private readonly PromotionalPurchaseSpecification promotionalPurchaseSpecification;
    private readonly CreditCardSpecification creditCardSpecification;
    private readonly WiretransferSpecification wiretransferSpecification;
    private readonly FreePurchaseSpecification freePurchaseSpecification;

    public PlaceOrderPage(IWebDriver driver, PurchaseTestInput purchaseTestInput) : base(driver)
    {
        this.purchaseTestInput = purchaseTestInput;
        this.promotionalPurchaseSpecification = new PromotionalPurchaseSpecification(purchaseTestInput);
        this.wiretransferSpecification = new WiretransferSpecification(purchaseTestInput);
        this.creditCardSpecification = new CreditCardSpecification(purchaseTestInput);
        this.freePurchaseSpecification = new FreePurchaseSpecification();
    }

    public override string Url
    {
        get
        {
            return @"yourSiteUrl";
        }
    }

    public void ChoosePaymentMethod()
    {
        if (this.creditCardSpecification.
        And(this.wiretransferSpecification.Not()).
        And(this.freePurchaseSpecification.Not()).
        And(this.promotionalPurchaseSpecification.Not()).
        IsSatisfiedBy(this.purchaseTestInput))
        {
            this.CreditCard.SendKeys("371449635398431");
            this.SecurityNumber.SendKeys("1234");
        }
        else
        {
            this.Wiretransfer.SendKeys("pathToFile");
        }
    }
}