How do you do Real-world Unit Testing?

I often hear about the benefits of unit-testing and how great it is to have a complete test suite and so on, but I've many times found it way too cumbersome to actually make unit-tests for the code I write.

For simple functions that only operate on scalables and return scalables, unit-testing is easy. However, it becomes a wildly different story when things like database connections, configuration files, memcached servers etc. are in play.

How do you test something like an IRC connection? Obviously you could set up a phony socket which doesn't really use the network, but that would in some cases defeat part of the test.

Dear YC, how do I make unit-tests with auxiliary resources?