Most of the base system on Linuxes (which is GNU) certainly have unit tests and static analyzers run on them, to the best of my knowledge (just looked at the coreutils). Most of these programs were maintained by Cygnus, and now by Red Hat after they acquired them.
less is an exception to the rule, as it's a small, standalone program and not as critical. Its initial development start seems to predate the official announcement of the GNU Project. I don't think most people really expend much thought on something like a pager.
EDIT: Brute forcing is also a very pragmatic approach. Ken Thompson uttered his famous adage for a reason, even if it was somewhat humorous.
less is an exception to the rule, as it's a small, standalone program and not as critical. Its initial development start seems to predate the official announcement of the GNU Project. I don't think most people really expend much thought on something like a pager.
EDIT: Brute forcing is also a very pragmatic approach. Ken Thompson uttered his famous adage for a reason, even if it was somewhat humorous.