Here are some hints about testing modifications to macro packages and
manual pages.

1. Use groff's '-ww' option to catch potential problems.
   Ideally, there shouldn't be any warnings.

2. For a well-formedness check, run doclifter (http://catb.org/~esr/doclifter)
   against your page.  This tool was written to lift pages to XML, but as a 
   side effect it acts as a validator that will warn you of potential problems 
   and non-portable constructs.

3. The two most important groff client types are X terminal emulators 
   and Postscript printers.  Eyeball-check your output under both.

4. The colorized man output of the Midnight Commander (what you get by 
   pressing the F3 key on a man page) is good for making small errors
   more visible.

5. Try different terminal line lengths, say, 80 and 100 characters.