Django: How to create a model dynamically just for testing


Question

I have a Django app that requires a settings attribute in the form of:

RELATED_MODELS = ('appname1.modelname1.attribute1',
                  'appname1.modelname2.attribute2', 
                  'appname2.modelname3.attribute3', ...)

Then hooks their post_save signal to update some other fixed model depending on the attributeN defined.

I would like to test this behaviour and tests should work even if this app is the only one in the project (except for its own dependencies, no other wrapper app need to be installed). How can I create and attach/register/activate mock models just for the test database? (or is it possible at all?)

Solutions that allow me to use test fixtures would be great.

1
60
2/2/2009 11:35:52 AM

Accepted Answer

You can put your tests in a tests/ subdirectory of the app (rather than a tests.py file), and include a tests/models.py with the test-only models.

Then provide a test-running script (example) that includes your tests/ "app" in INSTALLED_APPS. (This doesn't work when running app tests from a real project, which won't have the tests app in INSTALLED_APPS, but I rarely find it useful to run reusable app tests from a project, and Django 1.6+ doesn't by default.)

(NOTE: The alternative dynamic method described below only works in Django 1.1+ if your test case subclasses TransactionTestCase - which slows down your tests significantly - and no longer works at all in Django 1.7+. It's left here only for historical interest; don't use it.)

At the beginning of your tests (i.e. in a setUp method, or at the beginning of a set of doctests), you can dynamically add "myapp.tests" to the INSTALLED_APPS setting, and then do this:

from django.core.management import call_command
from django.db.models import loading
loading.cache.loaded = False
call_command('syncdb', verbosity=0)

Then at the end of your tests, you should clean up by restoring the old version of INSTALLED_APPS and clearing the app cache again.

This class encapsulates the pattern so it doesn't clutter up your test code quite as much.

51
11/3/2014 8:58:02 PM

@paluh's answer requires adding unwanted code to a non-test file and in my experience, @carl's solution does not work with django.test.TestCase which is needed to use fixtures. If you want to use django.test.TestCase, you need to make sure you call syncdb before the fixtures get loaded. This requires overriding the _pre_setup method (putting the code in the setUp method is not sufficient). I use my own version of TestCase that let's me add apps with test models. It is defined as follows:

from django.conf import settings
from django.core.management import call_command
from django.db.models import loading
from django import test

class TestCase(test.TestCase):
    apps = ()

    def _pre_setup(self):
        # Add the models to the db.
        self._original_installed_apps = list(settings.INSTALLED_APPS)
        for app in self.apps:
            settings.INSTALLED_APPS.append(app)
        loading.cache.loaded = False
        call_command('syncdb', interactive=False, verbosity=0)
        # Call the original method that does the fixtures etc.
        super(TestCase, self)._pre_setup()

    def _post_teardown(self):
        # Call the original method.
        super(TestCase, self)._post_teardown()
        # Restore the settings.
        settings.INSTALLED_APPS = self._original_installed_apps
        loading.cache.loaded = False

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