Trying out new test system

Covered working part of logic.c file
That is logic_create and logic_destroy functions

Decided to test for pointer validity as it is described in McConnel's *Perfect Code*

Decided to nullify pointer after logic_destroy.
So now I should pass pointer to pointer to struct into it.
Probably that's not a good solution.

Drawbacks:
 # assert does not work with NDEBUG
 # pointer address can still point to memory which is not available to read
    so it can lead to segmentation fault anyway, and code becames messier
 # that does not prevent me from storing old address somewhere else

Going to think about it and probably going to revert back.