'L{StringListMailbox.undeleteMessages} causes any messages marked for
deletion to be returned to their original state.'

def test_undeleteMessages(self):

    mailbox = mail.maildir.StringListMailbox(['foo'])
    mailbox.deleteMessage(0)
    mailbox.undeleteMessages()
    self.assertEqual(mailbox.listMessages(0), 3)
    self.assertEqual(mailbox.listMessages(), [3])
