public void FromXmlTest()
        {
            /*
             * Assume:     ToXml(string) is correct.
             */
            var authResponse = new AuthResponse();
            var xml          = XElement.Parse(File.ReadAllText(Data.AuthResponseXml)).Elements().ToArray();

            // Validate null argument.
            Assert.Throws <ArgumentNullException>("element", () => authResponse.FromXml(null));

            // XML must be same after loading and deserializing it.
            foreach (var element in xml)
            {
                authResponse.FromXml(element);
                Assert.True(XNode.DeepEquals(element, authResponse.ToXml("AuthRes")));
            }
        }