Localhost traffic doesn't appear in Charles
Some systems are hard coded to not use proxies for localhost traffic. Specifically IE 7 and .Net applications have this feature.
The workaround is to connect to http://localhost./test/ instead (note the . after localhost). This should work identically to localhost normally but with the advantage that it will go through Charles.
Alternatively you can replace localhost with the name of your machine, or your local link IP address (eg. 192.168.1.2). So rather than connecting to http://localhost/test/ you connect to http://machinename/test/