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.