Test-Driven Development with Django & South

I’d basically given up on attempting test-driven with Django, given the project I’m currently working on uses models with a lot of South migrations. Just building the database and running the migrations could take a minute or so when running manage.py test, and resetting the database to a clean state meant the test suite would take several minutes to run.

I’ve had an idea in the back of my mind for a while, and today I finally got around to making it work.

SQLite

When using SQLite, the test runner doesn’t bother to actually hit the filesystem, it just does the whole thing in memory, which is a good deal quicker. Previously, I couldn’t use SQLite, because South doesn’t like it (since SQLite doesn’t support ALTER TABLE).

My realisation was that if I turned off South, I could use SQLite, which I did with this rather hackish file called test_settings.py:

from settings import *

INSTALLED_APPS = [app for app in INSTALLED_APPS if app != 'south']

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': 'test_database.db'
    }
}

I can then do a quick run of the test suite using:

manage.py test --settings=test_settings

Obviously, this doesn’t run through my South migrations, which I probably should do from time to time (especially when adding new migrations). I can still test those with:

manage.py test

since by default the test runner will hit my normal settings module, which still has South in INSTALLED_APPS, and which hits my MySQL database.

The Results

With my test_settings, I get the following output:

Ran 121 tests in 3.218s

With my default settings, I get:

Ran 121 tests in 326.742s

If I run tests for a particular app (which is generally all I need to do), that difference is 0.312s to 31.064s.

That makes my test run approximately 99% quicker, and well within what I consider an acceptable time to run every time I make small changes to my code.

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