public void GetLastPaymentByEmail()
        {
            var arr = billingClient.GetLastPaymentByEmail("*****@*****.**");
            var p   = arr.ElementAt(0);

            Assert.AreEqual(p.ProductName, "1-30 users - Teamlab Server Enterprise Edition One Year Subscription");
            Assert.AreEqual(p.StartDate, new DateTime(2014, 3, 28, 13, 4, 24));
            Assert.AreEqual(p.PaymentDate, new DateTime(2014, 3, 28, 13, 4, 24));
            Assert.AreEqual(p.EndDate, new DateTime(2015, 3, 28, 13, 4, 24));
            Assert.IsTrue(p.SAAS);
        }