Re: Fwd: [Haskell-cafe] Data.Tree.Zipper in the standard libraries

It's not wasted work. As far as I know, only Ian advocates against including tests. Having worked on several data structure libraries, I've found that QuickCheck regularly catches errors that appear, and ensure over the long term that code remains stable. -- Don kr.angelov:

In this case the recommendation to write QuickCheck tests should be removed from the library submission procedure. I don't want to do wasted work again!

On Sat, May 31, 2008 at 1:16 PM, Ian Lynagh wrote:

...

So just to check, this proposal is to add Data.Tree.Zipper to containers and the QC tests to the testsuite, right?

As I've explained before[1], I don't think that QuickCheck tests are a good way to test libraries: They tend to test the same inputs (e.g. []) or equivalent inputs (e.g. "insert 2 [3]" and "insert 3 [4]") many times, meaning it takes much longer to get the same level of testing as a few well-chosen unit tests. When you multiply this by all the libraries the testsuite is meant to test, this is a significant amount of time.

I also don't think that adding the tests but not running them automatically is a good idea, as they will most likely just bitrot.

Adding a unit test for the bug you found is certainly a good idea, though!

[1] http://www.haskell.org/pipermail/libraries/2008-April/009594.html

Thanks Ian

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