Modify Installed_Apps settings

[Andrew Pinkham]

I have an app in Django 1.7.4 that I would like to use purely for testing.

$ ./manage.py startapp override

The app contains its own model, view, and URL pattern (the model overrides a model in another app, allowing me to test behavior in a specific case).

For the moment, I have the app in INSTALLED_APPS, and the tests run fine. However, I would like to remove the app from INSTALLED_APPS, and override the setting just for the tests. In theory:

@modify_settings(INSTALLED_APPS={'append': 'override'})

However, if I then remove the string from project_name/settings.py, I am given a Python Traceback which ends in:

django.db.utils.OperationalError: no such table: override_modelname

How may I force the TestCase class to apply the migration file override/migrations/0001_initial.py to the test database?

Thanks,
Andrew

[Joel Goldstick]

> --
In the book "Two Scoops of Django" there is a section about setting up
different settings files. That may help you out

http://twoscoopspress.org/pages/two-scoops-of-django-1-6-faq
--
Joel Goldstick
http://joelgoldstick.com

[Andrew Pinkham]

Thanks for the info, Joel.

However, I'm trying to avoid creating a separate settings file. Any info about how to properly use modify_settings to add to installed apps or how to force the test runner to apply a specific migration would still be appreciated.

Thanks,
Andrew

[Andrew Pinkham]

I am learning all sorts of things about Django's testing system (instead of actually getting work done).

The database schema is actually created via a call create_test_db() called on line 366 of setup_databases() in DiscoverRunner in django/test/runner.py. It's within this function, found in django/db/backends/base/creation.py, that migrate is called on available apps in Installed_Apps (via call_command!).

I was under the impression that code provided by TransactionTestCase was where the test database was (re-)created and destroyed throughout the lifetime of the test suite. As it turns out, while the code in TransactionTestCase loads and flushes data, it never touches the schema of the database (afaik).

This makes sense, as it seriously speeds up testing, as database creation is expensive.

Turns out, by simply overriding setUp and tearDown to use call_command with migrate, I can create the schema I desire.

# override/tests.py
from django.db import connections
from django.test import TestCase, override_settings, modify_settings
from django.core.management import call_command

@override_settings(
ROOT_URLCONF='override.urls')
@modify_settings(
INSTALLED_APPS={'prepend': {'override'}})
class OverrideTests(TestCase):

def setUp(self):
super().setUp()
for db in connections:
call_command(
'migrate',
'override',
verbosity=0,
interactive=False,
database=db,
test_flush=True)

def tearDown(self):
for db in connections:
call_command(
'migrate',
'override',
'zero',
verbosity=0,
interactive=False,
database=db,
test_flush=True)
super().tearDown()

This is, of course, quite slow, as each of my tests results in a database schema change.

I'm thus trying to get this working with setUpClass and tearDownClass.

@classmethod
def setUpClass(cls):
super().setUpClass()
for db in connections:
call_command(
'migrate',
'override',
verbosity=0,
interactive=False,
database=db,
test_flush=True)

@classmethod
def tearDownClass(cls):
for db in connections:
call_command(
'migrate',
'override',
'zero',
verbosity=0,
interactive=False,
database=db,
test_flush=True)
super().tearDownClass()

My understanding of TransactionTestCase (and the interaction with the decorators) makes me think this is possible, but at the moment, I'm getting the following error:

django.core.management.base.CommandError: App 'override' does not have migrations (you cannot selectively sync unmigrated apps)

I am also uncertain if this is a good idea, as I'm not clear as to whether TestCase will flush the data in the unexpected table (ie: will tests methods still be isolated?).

Any help or ideas welcome.

Andrew