Exploring test case fixtures in Django

Django has a nice feature for exploring the environment in which the tests run via the testserver command. You can give it paths to fixture files used in the test case you want and go crazy.

However, this use case becomes really unpleasant once you need to load bigger number of fixtures. It would be much more user friendly if you could instead tell it what test case you want to explore and the script automatically inferred what fixtures to load.

The --help output is silent on this, so let’s roll our own solution to this. The script will have two mandatory arguments: module containing the tests and the actual test case name.

run-test-server.py myapp.tests MyComplicatedTestCase

The first idea how to proceed is to simply import the module and look at fixtures attribute of the test case. Sadly, it is not that easy. Importing the module fails with ImproperlyConfiguredException because simply importing a module would be too much to ask for without loading all the Django settings. This could be a whole other rant.

Since __import__ is slightly more complicated that necessary, let’s offload the actual importing to importlib.import_module which works exactly as expected. However, it is only available since Python 2.7.

Once the module is imported, all that needs to be done is to retrieve the test case, its fixtures and fire out the testserver command with appropriate arguments.

The whole script looks as follows. The only unexplained part is the modification of path. This needs to be done so that the script can be located anywhere and still manage to import modules from current directory.

#! /usr/bin/env python

import argparse
from subprocess import call
import sys
import importlib

from django.conf import settings


def get_fixtures(module, case):
    settings.configure()
    parts = module.split('.')

    app = importlib.import_module(module)
    return getattr(app, case).fixtures


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument('MODULE', type=str)
    parser.add_argument('TEST_CASE', type=str)

    args = parser.parse_args()
    fixtures = get_fixtures(args.MODULE, args.TEST_CASE)

    call(["python", "manage.py", "testserver"] + fixtures)


if __name__ == '__main__':
    sys.path.append('.')
    main()

Further improvements

This script could obviously use a bit more polish:

• The help output could be more helpful.
• If something breaks, the user is presented with a stack trace. Not nice.