Sipsak

sipsak is a small comand line tool for developers and administrators of SIP applications. It can be used for some simple tests on SIP applications and devices.
sending OPTIONS request sending text files (which should contain SIP requests) traceroute (see section 11 in RFC3261) user location test flooding test random character trashed test interpret and react on response authentication with qop supported short notation supported for receiving (not for sending) string replacement in files can simulate calls in usrloc mode uses symmetric signaling and thus should work behind NAT
Available for Linux, BSD & Win32 SIPr: Open source SIP application testing framework (pronounced as "SIPPER") SIPp: Load testing tool Open Source VOIP Software