Thanks for your responses. Of course I already test every pure parts of my program easily. For now, user input is treated in 2 different ways: - direct IO with hgetLine and like functions (blocking) - the same but I directly push the strings on a TChan for another thread to treat them (not blocking). The second is easy to test, since all I have to do is to insert test strings on the TChan to simulate user's input. Maybe I can do everything this way. But for example I had a bug of two threads inter-blocked on the handle. These tests were not able to show it, since the test takes place not on the handle itself but a little after. Maybe "mock handle" can help. Corentin On Tue, Oct 26, 2010 at 11:32 PM, Antoine Latter wrote:

On Tue, Oct 26, 2010 at 11:11 AM, Dupont Corentin wrote:

...

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.

I haven't tested it yet, but this "mock handle" will eventually work in GHC 7:

http://hackage.haskell.org/trac/ghc/attachment/ticket/4144/ByteStringHandle....

At least, the bug report about how it didn't work has now been closed :-)

I don't remember which operations worked and which didn't - getChar would work, but getContents would fail.

The others have great advice, that you should try to isolate the logic of your code from IO for precisely this reason - so it is easily testable.

Antoine