Hi there, I have the following snippet: data Volume = Volume { name :: String , mount :: String , size :: String , fs :: String , mbr :: Bool } deriving (Show, Eq) defaultVolume :: Volume defaultVolume = Volume { name = "" , mount = "" , size = "" , fs = "ext4" , mbr = False } parseOptVols :: String -> Volume parseOptVols s = parseChain (defaultVolume, s) where parseChain = parseMBR . parseFS . parseSize . parseMount . parseName parseName (vol, s) = (vol {name = getThis s}, getNext s) parseMount (vol, s) = (vol {mount = getThis s}, getNext s) parseSize (vol, s) = (vol {size = getThis s}, getNext s) -- fs and mbr are optional parseFS (vol, "") = (vol, "") parseFS (vol, ',':s) = (vol, s) parseFS (vol, s) = (vol {fs = getThis s}, getNext s) parseMBR (vol, "t") = vol {mbr = True} parseMBR (vol, _ ) = vol getThis = takeWhile (',' /=) getNext = saveTail . dropWhile (',' /=) saveTail :: [a] -> [a] saveTail [] = [] saveTail (_:xs) = xs What it basically does is parse a string (handed over from the command line) like "boot,/boot,256M,ext3,t" and populates a Volume instance with this. The last two fields are optional. I like testing and coming from an object-oriented background unit testing is the most comfortable to me. But I wonder if there is some smart way to make QuickCheck produce test cases. I would need some generator for this which produces a pattern like "name,mount,size,fs,mbr" eventually leaving "fs" and/or "mbr" empty and sometimes omitting both commas or just one of them. And I also need access to these fields in order to be able to compare them with the resulting Volume instance. I can see how to achieve the former somehow, but I don't have any clue how to achieve the latter. Any hints? Or is this simply not a nail for the QuickCheck-hammer? Regards, Thomas Bach. PS: Any advice on how to improve the code above is highly appreciated as well.