'L{MaildirMailbox.appendMessage} returns a L{Deferred} which fires when
the message has been added to the end of the mailbox.'

def test_append(self):

    mbox = mail.maildir.MaildirMailbox(self.d)
    mbox.AppendFactory = FailingMaildirMailboxAppendMessageTask
    d = self._appendMessages(mbox, [('X' * i) for i in range(1, 11)])
    d.addCallback(self.assertEqual, ([None] * 10))
    d.addCallback(self._cbTestAppend, mbox)
    return d
