Hackers and Sysadmins :-)
Google has recently released "pactester", a tool to test proxy auto-configuration (PAC) files. Use of PAC files is becoming more and more common because of automation and ease of administration provided by them. Before pactester there was no "real" way to test the PAC files. We could tell whether this site will be accessible using this PAC file or not. But, we could not tell which proxy server will be used for a specific URL unless we examine the traffic using some network sniffer or check the access logs at the proxy server. Both of these ways were not very accessible and were time consuming. Of course, another way to test would be the manual inspection of PAC files, but again it's error prone and quite impractical for large and complex PAC files.
Project home page: http://code.google.com/p/pactester
Project download: http://http://code.google.com/p/pactester/downloads/list
Quick Documentation: http://pactester.googlecode.com/svn/trunk/README
Mailing list and discussion group: http://groups.google.com/group/pactester
Tested to works on: Linux, Mac OS X, Windows-Cygwin
Cheers to open source!! :-)
Manu Garg/http://www.manugarg.com/"Journey is the destination of life"
Update: Now there is an implementation of pactester in C using pacparser library. Compiled binary of pactester for Windows can be downloaded from pactester download page.