Better to leave it off. No reason to install an insecure program just because of a test. If you want telnet-style functionality, use ssh.
What I do: apt-get install ssh # Note: install server as daemon # disable crap in inetd apt-get -y remove --purge talkd telnetd fingerd pidentd biff ~mark > I can ping 127.0.0.1 but not telnet to it. I'm guessing telnet connectivity > is turned off by default. Where do I go to turn it on? I haven't used > telnet on my network before but it's suggested as a test in a HOW-TO I'm > working through.