Nose test script with command line arguments

Question

I would like to be able to run a nose test script which accepts command line arguments. For example, something along the lines:

test.py

import nose, sys

def test():
    # do something with the command line arguments
    print sys.argv

if __name__ == '__main__':
    nose.runmodule()

However, whenever I run this with a command line argument, I get an error:

$ python test.py arg
E
======================================================================
ERROR: Failure: ImportError (No module named arg)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/nose-0.11.1-py2.6.egg/nose/loader.py", line 368, in loadTestsFromName
    module = resolve_name(addr.module)
  File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/nose-0.11.1-py2.6.egg/nose/util.py", line 334, in resolve_name
    module = __import__('.'.join(parts_copy))
ImportError: No module named arg

----------------------------------------------------------------------
Ran 1 test in 0.001s

FAILED (errors=1)

Apparently, nose tries to do something with the arguments passed in sys.argv. Is there a way to make nose ignore those arguments?

Answer 1

Alright, I hate "why would you want to do that?" answers just as much as anyone, but I'm going to have to make one here. I hope you don't mind.

I'd argue that doing whatever you're wanting to do isn't within the scope of the framework nose. Nose is intended for automated tests. If you have to pass in command-line arguments for the test to pass, then it isn't automated. Now, what you can do is something like this:

import sys

class test_something(object):
    def setUp(self):
        sys.argv[1] = 'arg'
        del sys.argv[2] # remember that -s is in sys.argv[2], see below
    def test_method(self):
        print sys.argv

If you run that, you get this output:

[~] nosetests test_something.py -s
['/usr/local/bin/nosetests', 'arg']
.
----------------------------------------------------------------------
Ran 1 test in 0.001s

OK

(Remember to pass in the -s flag if you want to see what goes on stdout)

However, I'd probably still recommend against that, as it's generally a bad idea to mess with global state in automated tests if you can avoid it. What I would likely do is adapt whatever code I'm wanting to test to take an argv list. Then, you can pass in whatever you want during testing and pass in sys.argv in production.

UPDATE:

The reason why I need to do it is because I am testing multiple implementations of the same library. To test those implementations are correct I use a single nose script, that accepts as a command line argument the library that it should import for testing.

It sounds like you may want to try your hand at writing a nose plugin. It's pretty easy to do. Here are the latest docs.

Answer 2

You could use another means of getting stuff into your code:

import os

print os.getenv('KEY_THAT_MIGHT_EXIST', default_value)

Then just remember to set your environment before running nose.

Answer 3

I think that is a perfectly acceptable scenario. I also needed to do something similar in order to run the tests against different scenarios (dev, qa, prod, etc) and there I needed the right URLS and configurations for each environment.

The solution I found was to use the nose-testconfig plugin (link here). It is not exactly passing command line arguments, but creating a config file with all your parameters, and then passing this config file as argument when you execute your nose-tests.

The config file has the following format:

[group1]
env=qa

[urlConfig]
address=http://something

[dbConfig]
user=test
pass=test

And you can read the arguments using:

from testconfig import config

print(config['dbConfig']['user'])

Answer 4

For now I am using the following hack:

args = sys.argv[1:]
sys.argv = sys.argv[0:1]

which just reads the argument into a local variable, and then deletes all the additional arguments in sys.argv so that nose does not get confused by them.

Answer 5

Just running nose and passing in parameters will not work as nose will attempt to interpret the arguments as nose parameters so you get the problems you are seeing.

I do not think nose support parameter passing directly yet but this nose plug-in nose-testconfig Allows you to write tests like below:

from testconfig import config
def test_os_specific_code():
    os_name = config['os']['type']
    if os_name == 'nt':
        pass # some nt specific tests
    else:
        pass # tests for any other os