This won't be a full post, but just a quick note (probably the first one of a serie) about development with Django.
When we write a TestCase test, if we have defined a setUp method, it will be called before the execution of each test. One could think that the database is completely reset after each test, but this is not true (not like I was thinking). After each test, whatever we wrote on the database is rolled back. If we create a "Client" row (assuming we have a model called Clients) in our setUp, when we call it the second time the ID won't be 1 as someone (me included) could expect. It will be 2 instead, because the database has not completely deleted and created from scratch.
This means that we can't assume that our Client ID will always be 1 for each test and we should rather reference to it in a dinamic way like: self.client.id
This could be a trivial thing for many people but I was not 100% sure about this so I asked for a confirmation on #django IRC room and people (expecially apollo13) was kind enough to explain me how it works.