Extracting unit tests from REPL sessions

I find writing test cases the most boring thing in the world, and I think I'm not alone. Obviously, I test my code interactively in REPL as I write it. It shouldn't be very hard to take a log of my REPL sessions and automatically write test cases based on that. The only thing I found was this paper, which describes exactly the functionality I want (for Ruby). However, I haven't been able to find the actual code anywhere.

I mainly use Ruby, Scala, Haskell and Clojure, but I'd like to hear about any language that has such a functionality implemented.