manage.py test command that accepts --app_prefix argument and if given test only apps with names starting with this prefix. App names are got from INSTALLED_APPS. This is suitable to test only apps from your project (which are usually prefixed with poreject name), not third-party apps.
Let's set INSTALLED_APPS as:
INSTALLED_APPS = (
'my_project.apps.blog',
'my_project.apps.news',
'south',
'registration',
'my_project.apps.catalog',
'sorl.thumbnail',
)
Then after python manage.py test --app_prefix=my_project.apps only blog, news and catalog will be tested.
You can (thougn it doesn't make a lot of sense) list apps and then filter them with --app_prefix. For example, python manage.py test blog news south registration --app_prefix=my_project.apps will test only blog and news.