'When L{NTTPServer} receives a I{XROVER} command, it sends a list of
I{References} header values for the messages in a particular group (RFC
2980, section 2.11).'

def test_XROVER(self):

    self.server.do_GROUP('alt.test.nntp')
    self.transport.clear()
    self.server.do_XROVER()
    self.assertEqual(self.transport.value().split('\r\n'), ['221    Header    follows', '.', ''])
