Run test with different database

settings.py

import sys
import os

# ...
# settings.py extra configurations
# ...

if sys.argv[1] == 'test':
    DATABASES = {
        'default': {
            'ENGINE': 'django.db.backends.sqlite3',
            'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
        }
    }
else:
    DATABASES = {'default': 'psql://user:password@server:5432/database'}