stool testing cannot detect IBD

The only two tests for IBD are
1) necropsy
2) liver biopsy

both of which are not the sort of thing that you'd want to put your snake through without compelling evidence as to it's need.

on the other hand though, stool testing on any new snake is a prudent course of action. it won't detect IBD but it will detect many other (and much more common) problems.