def testSMTPGreetingHost(self, serverClass=smtp.SMTP):
        """
        Test that the specified hostname shows up in the SMTP server's
        greeting.
        """
        s = serverClass()
        s.host = b"example.com"
        t = StringTransport()
        s.makeConnection(t)
        s.connectionLost(error.ConnectionDone())
        self.assertIn(b"example.com", t.value())

        Test that the specified hostname shows up in the SMTP server's
        greeting.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/test/test_smtp.py