There was a study that did a line by line translation of 4 python projects to haskell and caught some bugs (between 0 and 4 per project): http://evanfarrer.blog

There was a study that did a line by line translation of 4 python projects to haskell and caught some bugs (between 0 and 4 per project): http://evanfarrer.blogspot.co.uk/2012/06/unit-testing-isnt-enough-you-need.html http://evanfarrer.blogspot.co.uk/2012/06/unit-testing-isnt-e... I got the impression that the bugs found were either not at all serious (e.g. throwing a typeerror on malformed input instead of some other nicer kind of error) or were in areas of the code not covered by tests. Unfortunately the author does not rate them by severity.