def test_ignoreUnknownCredInterfaces(self):
        """
        L{SSHUserAuthServer} sets up
        C{SSHUserAuthServer.supportedAuthentications} by checking the portal's
        credentials interfaces and mapping them to SSH authentication method
        strings.  If the Portal advertises an interface that
        L{SSHUserAuthServer} can't map, it should be ignored.  This is a white
        box test.
        """
        server = userauth.SSHUserAuthServer()
        server.transport = FakeTransport(self.portal)
        self.portal.registerChecker(AnonymousChecker())
        server.serviceStarted()
        server.serviceStopped()
        server.supportedAuthentications.sort() # give a consistent order
        self.assertEqual(server.supportedAuthentications,
                          [b'password', b'publickey'])

        L{SSHUserAuthServer} sets up
        C{SSHUserAuthServer.supportedAuthentications} by checking the portal's
        credentials interfaces and mapping them to SSH authentication method
        strings.  If the Portal advertises an interface that
        L{SSHUserAuthServer} can't map, it should be ignored.  This is a white
        box test.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/test/test_userauth.py