Some time ago, I watched James Tauber’s talk at DjangoCon about Pinax, a collection of re-usable Django applications. If you are thinking of a collection as a bunch of apps carelessly thrown together, you could not be more mistaken. Pinax is the foundation for a complete social networking site which covers most features you can imagine, the whole nine yards.
Forget django-admin.py startproject! Just do cp pinax myproject, remove some stuff you don’t need, adjust the templates and you are done!
Ok, I might be exagerating a bit, but watch the talk to build your own opinion.
I’m currently rewriting dwidder  and I just spent way to much time on a unit test for the registration view. These are the things that made me stumble:
Write fixtures. Unit tests run on an empty database. Somewhere deep in your code might be a reference to one of the default applications, like django.contrib.sites, which will fail, because there is no default site object in your database.
Don’t subclass unittest.TestCase. Use Django’s TestCase class instead. Otherwise you will miss all the fancy stuff, like automatic fixture loading.
Import mail, not outbox. Django provides a dummy email outbox. But to make it work as expected, you have to import the mail module. If you import the outbox directly, it will always be empty.
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