[TIP] Fwd: Mocking with "mock" in unit testing

[James Chapman]

Originally sent to python tutor mailing list but I suspect this might be a
better list for my question...

Hi all

I have a question regarding mocking in unit testing.

Let's assume I have the following class:

-------------------------------------------
import subprocess

class Pinger(object):

    def ping_host(self, host_to_ping):
        cmd_string = 'ping %s' % (host_to_ping)
        cmd_args = cmd_string.split()
        proc = subprocess.Popen(cmd_args, shell=True)
        proc.wait()
        if proc.returncode != 1:
            raise Exception('Error code was: %d' % (proc.returncode))

-------------------------------------------


In my unittest I don't want to run the ping command, (It might not be
available on the build system) I merely want to check that a call to
subprocess.Popen is made and that the parameters are what I expect?

So far I have this, but it doesn't work and I suspect it's way off!!


-------------------------------------------
 import mock
import unittest
from tutor_q import Pinger

class Test_Pinger(unittest.TestCase):

    def test_ping_host(self):
        pinger = Pinger()
        assert pinger
        subprocess = mock.Mock()
        subprocess.Popen.return_value = 0
        subprocess.assert_called_once_with(['ping','localhost'])
        pinger.ping_host('127.0.0.1')




if __name__ == '__main__':
    unittest.main()

-------------------------------------------


Can anyone point me in the right direction on how to mock up these
subprocess calls?

Thanks

James
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