sanity check

sanity check n.  1. The act of checking a piece of code (or
   anything else, e.g., a Usenet posting) for completely stupid
   mistakes.  Implies that the check is to make sure the author was
   sane when it was written; e.g., if a piece of scientific software
   relied on a particular formula and was giving unexpected results,
   one might first look at the nesting of parentheses or the coding of
   the formula, as a `sanity check', before looking at the more
   complex I/O or data structure manipulation routines, much less the
   algorithm itself.  Compare {reality check}.  2. A run-time test,
   either validating input or ensuring that the program hasn't screwed
   up internally (producing an inconsistent value or state).