def METHOD_NAME(self):
    source = "Subject: test\r\n\r\ntest body\r\n"
    expected = source
    msg = self.msgmaker(self.typ(source))
    s = self.ioclass()
    g = self.genclass(s, policy=policy.SMTP)
    g.flatten(msg)
    self.assertEqual(s.getvalue(), self.typ(expected))