def test_uidnext(self):
        """
        If the server response to a I{SELECT} or I{EXAMINE} command includes an
        I{UIDNEXT} response, the L{Deferred} returned by L{IMAP4Client.select}
        or L{IMAP4Client.examine} fires with a C{dict} including the value
        associated with the C{'UIDNEXT'} key.
        """
        d = self._examineOrSelect()
        self._response(b'* OK [UIDNEXT 4392] Predicted next UID')
        self.assertEqual(
            self.successResultOf(d),
            {'READ-WRITE': False, 'UIDNEXT': 4392})

        If the server response to a I{SELECT} or I{EXAMINE} command includes an
        I{UIDNEXT} response, the L{Deferred} returned by L{IMAP4Client.select}
        or L{IMAP4Client.examine} fires with a C{dict} including the value
        associated with the C{'UIDNEXT'} key.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/test/test_imap.py