[TIP] argv with unitest

Matt Harrison matthewharrison at gmail.com
Sun Sep 6 09:59:30 PDT 2009

On Sun, Sep 6, 2009 at 6:53 AM, Mag Gam<magawake at gmail.com> wrote:
> I have tried using the
> http://www.artima.com/weblogs/viewpost.jsp?thread=4829 for a reference
> but I am still having problems,
> I think I should take couple of steps back....and write some
> pseudocode for a good testing framework template.
> Foo.pl -- The purpose is to to count from 1 to 100
> Arguments
> --help -h
> --stdout -s
> --stderr -e
> Should raise an exception if a wrong argument was given and run a
> Usage() function
> I would invoke it like this:
> python Foo.pl --stdout outfile --stderr errorfile
> My tests would be like this:
> If stdout is set, will it create a file of stdout?
> If --help or -h is set the Usage() call should be called and return an
> error code 1
> If --help and --stdout is set --help should over ride and still return
> an error code 1
> How can I incorporate this to a good testing framework?

I would advocate non calling sys.exit from the main function.  Only
call if from here

if __name__ == '__main__':

Then have main return the exit code you want.

As far as testing a doctest would look something like this:

>>> main(['--stdout', 'outfile'])
>>> print open('outfile').read()

A unittest would look similar

import unittest
class TestCount(unittest.TestCase):
  def test_count(self):
    main(['--stdout', 'outfile'])
    results = open('outfile').read()
    self.assertEqual(results, '0\n1\n2\n....)

if __name__=='__main__':

I gave a talk about best practices for writing scripts which includes
testing examples.  Newer slides are here[0] video is here[1].

good luck,


0 - http://panela.blog-city.com/oscon_scripting_with_python_handout.htm
1 - http://us.pycon.org/2009/conference/schedule/event/61/

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