[Haskell-cafe] Test command line programs

Hello again café, I have a command line program that takes input from various handles (actually network sockets) like this:

s <- hGetLine h etc.

I'd like to unit test this. How can I do? I'd like to inject data on the handle so that all the input chain is tested. How are command line programs' IO automatically tested usually? Another little question: How can I access the name of a function inside a function (for Trace purpose)? I have to use the CPP preprocessor? Thanks for hints, Corentin