HI there,
Are your sure that your freeradius server is up? Try to start freeradius in debug mode and make the radtest again:
sudo freeradius -X
radtest bob bob localhost 1812 testing
If you get an error trying to start the server with "sudo freeradius -X" try to stop it and start+test again:
killall freeradius
sudo freeradius -X
radtest bob bob localhost 1812 testing
As James said you need to run in debug mode while tetsing...so you can check whats going on.
Cheers,
Shirkavand