public void Saml2StatementExtensions_ToXElement_SessionNotOnOrAfter()
        {
            Saml2AuthenticationStatement assertion =
                new Saml2AuthenticationStatement(
                    new Saml2AuthenticationContext(
                        new Uri("urn:oasis:names:tc:SAML:2.0:ac:classes:unspecified")));

            assertion.SessionNotOnOrAfter = DateTime.UtcNow;

            var xml = assertion.ToXElement();

            xml.Attribute("SessionNotOnOrAfter").Value.Should().Be(assertion.SessionNotOnOrAfter.Value.ToSaml2DateTimeString());
        }