def test_outbox_login(): o = Outbox('username', 'password', 'server', 1234) with mock.patch('smtplib.SMTP') as SMTP: smtp = SMTP.return_value o._login() print(smtp.mock_calls) smtp.set_debuglevel.assert_any_call(False) smtp.starttls.assert_any_call() smtp.login.assert_any_call('username', 'password')