How to test a firewall with NAT?

[Gregory Edigarov]

Hello Everybody,

I am trying to move one of my servers/routers from linux/iptables to 
freebsd/pf, and need a methodology of testing the pf firewall ruleset 
before it will  go in production.  I cannot  experiment on live network, 
because it's a busy server.

I only have one other machine available.
What can I do and what tool can you recommend?

Thank you.
--
With best regards,
    Gregory Edigarov