'L{twisted.mail.smtp.sendmail} will pass through the message untouched
if it is a file-like object.'

def test_messageFilePassthrough(self):

    reactor = MemoryReactor()
    messageFile = BytesIO('File!')
    smtp.sendmail('localhost', 'source@address', 'recipient@address', messageFile, reactor=reactor)
    factory = reactor.tcpClients[0][2]
    self.assertIs(factory.file, messageFile)
