def test_xid_to_string(self):
        from psycopg2.extensions import Xid

        x1 = Xid.from_string('42_Z3RyaWQ=_YnF1YWw=')
        self.assertEqual(str(x1), '42_Z3RyaWQ=_YnF1YWw=')

        x2 = Xid.from_string('99_xxx_yyy')
        self.assertEqual(str(x2), '99_xxx_yyy')

    def test_xid_from_string(self):
        from psycopg2.extensions import Xid

        x2 = Xid.from_string('42_Z3RyaWQ=_YnF1YWw=')
        self.assertEqual(42, x2.format_id)
        self.assertEqual('gtrid', x2.gtrid)
        self.assertEqual('bqual', x2.bqual)

        x3 = Xid.from_string('99_xxx_yyy')
        self.assertEqual(None, x3.format_id)
        self.assertEqual('99_xxx_yyy', x3.gtrid)
        self.assertEqual(None, x3.bqual)