I am new to squid and ordered 'squid: the definitive guide' book. I was wondering if it is possible to test squid using only one machine?

Thanks for any help.

Yes. I use squid on my desktop machine. You just have to make sure that whatever connection you are using gets passed through the proxy. Right now I am using it as a proxy filter (with squid guard) for firefox. It is just like any other proxy. It works quite well.

bcwagne : how did you configure squid ,by default ?

Yes. I left all the default settings alone, except for the ones mentioning which IP address to listen on, and the url_rewrite_program tag, which I changed to squidguard. It is possible to set up squid as a transparent proxy (so you don't have to configure each machine connected to it), but I didn't bother as I am only using one machine, and it isn't a big deal to configure a few programs for the proxy.

I didn't set up the caching for squid.

I mostly followed the Ubuntu squid how to.

first of all, you have to change the sittings of your browser to use your machine as a proxy. the default sitting of the SQUID is listening to port 3128.

you may just use (no need to change) the following lines in the /etc/squid/squid.conf:
http_port 3128 -> the listening port, you can change to 8080 or just use it as it is
acl all src 0.0.0.0/0.0.0.0 -> refer to all connection
acl localhost src 127.0.0.1/255.255.255.255 -> the connection form local machine

run the SQUID (/etc/init.d/squid start), and try to access the web. it should work.

now, in the rules section (http_access), you may change the following (i highly recommend to comment with '#' instead to changing the statements):
http_access allow localhost -> http_access deny localhost
now, update the new configuration to running SQUID (/etc/init.d/squid reload) (fast), or you may restart it (/etc/init.d/squid restart) (very slow). try to access the web again. it should not allow you now (really, I did not try it).

NOTE: that the parsing of the rules is from top to bottom. i.e., the system will read the rules one by one from top to bottom, once a match found it will apply it (allow or deny) then stop. for example, if you move the line "http_access deny all" to the top of rule section, no one will be able to use the system.

also, you may play in the Safe_ports by opening and closing ports such as opining only 80 and 443 to allow only web browsing.

hope this will help you.