ANN: SmallCheck 0.1
SmallCheck: another lightweight testing library in Haskell. Folk-law: if there is any case in which a program fails, there is almost always a simple one. SmallCheck is similar to QuickCheck (Claessen and Hughes 2000-) but instead of a sample of randomly generated values, SmallCheck tests properties for all the finitely many values up to some depth, progressively increasing the depth used. For data values, depth means depth of construction. For functional values, it is a measure combining the depth to which arguments may be evaluated and the depth of possible results. Other possible sales pitches: * write test generators for your own types more easily * be sure any counter-examples found are minimal * write properties using existentials as well as universals * establish complete coverage of a defined test-space * display counter-examples of functional type A new version of SmallCheck can be obtained from: http://www.cs.york.ac.uk/fp/smallcheck0.1.tar The differences from 0.0 are two fixes (space-fault, output buffering), an 'unsafe' but sometimes useful Testable (IO a) instance and additional examples. Comments and suggestions welcome. Colin R
colin:
SmallCheck: another lightweight testing library in Haskell.
Folk-law: if there is any case in which a program fails, there is almost always a simple one.
SmallCheck is similar to QuickCheck (Claessen and Hughes 2000-) but instead of a sample of randomly generated values, SmallCheck tests properties for all the finitely many values up to some depth, progressively increasing the depth used. For data values, depth means depth of construction. For functional values, it is a measure combining the depth to which arguments may be evaluated and the depth of possible results.
Other possible sales pitches: * write test generators for your own types more easily * be sure any counter-examples found are minimal * write properties using existentials as well as universals * establish complete coverage of a defined test-space * display counter-examples of functional type
A new version of SmallCheck can be obtained from: http://www.cs.york.ac.uk/fp/smallcheck0.1.tar The differences from 0.0 are two fixes (space-fault, output buffering), an 'unsafe' but sometimes useful Testable (IO a) instance and additional examples.
Comments and suggestions welcome.
I've written a lambdabot plugin for SmallCheck, to go with the existing one for QuickCheck. It's running on #haskell now (after removing that pesky Testable IO instance (not good for security...). Let's run QuickCheck (check) head to head with SmallCheck (scheck): $ ./lambdabot Initialising plugins ................................................. done. lambdabot> check True OK, passed 500 tests. lambdabot> scheck True Completed 1 test(s) without failure. lambdabot> check \s -> (s :: [Int]) == (reverse . reverse) s OK, passed 500 tests. lambdabot> scheck \s -> (s :: [Int]) == (reverse . reverse) s Completed 623530 test(s) without failure. lambdabot> check \s -> not (null s) ==> minimum (s :: [Int]) == (head . sort) s OK, passed 500 tests. lambdabot> scheck \s -> not (null s) ==> minimum (s :: [Int]) == (head . sort) s Completed 623530 test(s) without failure. But 1 did not meet ==> condition. lambdabot> scheck \s -> not (null s) ==> minimum (s :: [Int]) == (last . sort) s Failed test no. 10. Test values follow.: [-1,-1,-1,-1,-1,-1,-1,0] lambdabot> check \s -> not (null s) ==> minimum (s :: [Int]) == (last . sort) s Falsifiable, after 1 tests: [2,1] One thing needed for online use: some more instances for the various numeric types might be useful, Float, Double, Ratio, Complex etc. -- Don
Don,
Let's run QuickCheck (check) head to head with SmallCheck (scheck): ... lambdabot> scheck \s -> not (null s) ==> minimum (s :: [Int]) == (last . sort) s Failed test no. 10. Test values follow.: [-1,-1,-1,-1,-1,-1,-1,0]
lambdabot> check \s -> not (null s) ==> minimum (s :: [Int]) == (last . sort) s Falsifiable, after 1 tests: [2,1]
So your plugin is based on depthCheck 8, not the iterative deepening of smallCheck; otherwise smallCheck would report [-1,0] as the first failure. I'll add a 'batch' version of iterative deepening.
One thing needed for online use: some more instances for the various numeric types might be useful, Float, Double, Ratio, Complex etc.
Fair point. I admit that I rarely use numbers other than the non-negative integers when programming. Even deciding to include -1 in the default Int series was a trip into an alien world. :-) I'll add some simple default instances for other numeric types used by the more arithmetically adventurous. Colin
participants (2)
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Colin Runciman -
dons＠cse.unsw.edu.au