How to run Django's test database only in memory?

If you set your database engine to sqlite3 when you run your tests, Django will use a in-memory database.

I'm using code like this in my settings.py to set the engine to sqlite when running my tests:

if 'test' in sys.argv:
    DATABASE_ENGINE = 'sqlite3'

Or in Django 1.2:

if 'test' in sys.argv:
    DATABASES['default'] = {'ENGINE': 'sqlite3'}

And finally in Django 1.3 and 1.4:

if 'test' in sys.argv:
    DATABASES['default'] = {'ENGINE': 'django.db.backends.sqlite3'}

(The full path to the backend isn't strictly necessary with Django 1.3, but makes the setting forward compatible.)

You can also add the following line, in case you are having problems with South migrations:

    SOUTH_TESTS_MIGRATE = False

I usually create a separate settings file for tests and use it in test command e.g.

python manage.py test --settings=mysite.test_settings myapp

It has two benefits:

1. You don't have to check for test or any such magic word in sys.argv, test_settings.py can simply be

   from settings import *
   
   # make tests faster
   SOUTH_TESTS_MIGRATE = False
   DATABASES['default'] = {'ENGINE': 'django.db.backends.sqlite3'}
   

   Or you can further tweak it for your needs, cleanly separating test settings from production settings.

2. Another benefit is that you can run test with production database engine instead of sqlite3 avoiding subtle bugs, so while developing use

   python manage.py test --settings=mysite.test_settings myapp
   

   and before committing code run once

   python manage.py test myapp
   

   just to be sure that all test are really passing.

MySQL supports a storage engine called "MEMORY", which you can configure in your database config (settings.py) as such:

    'USER': 'root',                      # Not used with sqlite3.
    'PASSWORD': '',                  # Not used with sqlite3.
    'OPTIONS': {
        "init_command": "SET storage_engine=MEMORY",
    }

Note that the MEMORY storage engine doesn't support blob / text columns, so if you're using django.db.models.TextField this won't work for you.