def test_uris(self):
            """Test that URIs are invariant under the transformation."""
            invariant = [
                "ftp://ftp.is.co.za/rfc/rfc1808.txt",
                "http://www.ietf.org/rfc/rfc2396.txt",
                "ldap://[2001:db8::7]/c=GB?objectClass?one",
                "mailto:John.Doe@example.com",
                "news:comp.infosystems.www.servers.unix",
                "tel:+1-816-555-1212",
                "telnet://192.0.2.16:80/",
                "urn:oasis:names:specification:docbook:dtd:xml:4.1.2",
            ]
            for uri in invariant:
                self.assertEqual(uri, iri2uri(uri))