Especially to Johan and Milan, I'm thinking to introduce more automatic tests for the containers library. Let's take Data.Map as example: 1) doctest Some haddoc documents include the following style. -- > Data.Map.null (empty) == True If we modify it like -- >>> Data.Map.null (empty) -- True we can use doctest. And we can remove corresponding unit test from test/*-properties.hs. Note that I'm not sure how to specify errors with doctest at this moment. 2) test-framework-th If we replace "test_" with "case_", we can use test-framework-th to generate the long list of test cases. We don't need to update it when we add "prop_" and "case_". We can specify the number of QuickCheck test as follows: runghc -i.. -DTESTING map-properties.hs --maximum-generated-tests=500 Since this is test stuff, we don't have to add doctest and test-framework-th to containers.cabal. What do you think? If you like this, I will work and send you pull request. --Kazu