Comment # 23 from Gaetan Boisson

I think we really need 0 and NULL to be treated differently. It is important
for instance to define that a type of document cannot be issued to a certain
category of patrons, without falling back on a more generic rule that would
allow it.
Sometimes we also want to define that 0 books of that type can be issued to a
patron category, with a loan period of X days : if we force the loan on an
exceptional basis, the length of the loan will already be defined.

Here is my test plan so far: i have defined 8 rules, matching the 8
possibilities. For every rule i put the same value in each field:

8 for same library, same patron type, same item type
7 for same library, same patron type, all item types
6 for same library, all patron types, same item type
5 for same library, all patron types, all item types
4 for all libraries, same patron type, same item type
3 for all libraries, same patron type, all item types
2 for all libraries, all patron types, same item type
1 for all libraries, all patron types, all item types

the i tweak to put NULL (or 0 at the moment) at different places, loan some
books and see what happens.

So far one thing that turned out not to work out was the number of renewals :
it falls straight back to rule 3, and if i void rule 3 it falls back to rule 1,
ignoring rule 2.

There are a lot of possibilities to test and i am not done yet...