as i see it, if it specifies nothing you have two options, either you don't Set them or you Set them and test for them.
setting and not testing the errors seems wrong to me.
and if you look at other wine code error codes are tested all the time, and the variation in error codes of different windows versions is one of the most ocurrent fixes to tests.
you can argue if that's the correct approach or not, but that's for the comunity to achieve a consensus, which right now is testing for error codes.