Easy way to create fixtures that use betternestedset?

Other than calculating by hand the :lft and :rgt for my fixtures for classes that use betternestedset, is there an easier (automagic) way?

Thanks in advance,

Alan

http://nubyonrails.com/articles/2005/12/27/dump-or-slurp-yaml-reference-data http://snippets.dzone.com/tag/fixtures

Create your DB records in irb or some other ruby script file outside of rails in a temporary DB (or just use your existing DB), then use that to export the YAML from the live data.

Thanks!!