smallcheck is a testing library to verify properties for test cases to a certain depth. The depth for data values refers to the depth of nested constructors, while for functional values, it refers to the depth of nested case analysis and results. The test cases will be generated by smallcheck. It is now available on Fedora. Install it using:

 $ sudo yum install ghc-smallcheck-devel

The following BitAdd.hs example demonstrates the use of smallcheck:

import Test.SmallCheck

and2 (a,b)       = a && b

xor2 (a,b)       = a /= b

halfAdd (a,b)    = (sum,carry)
  where sum      = xor2 (a,b)
        carry    = and2 (a,b)

bit False        = 0
bit True         = 1

num []           = 0
num (a:as)       = bit a + 2 * num as

bitAdd a []      = [a]
bitAdd a (b:bs)  = s : bitAdd c bs
  where (s,c)    = halfAdd (a,b)

prop_bitAdd a as = num (bitAdd a as) == bit a + num as

main             = smallCheck 3 prop_bitAdd

We ask smallcheck to run tests to a depth of 3. You can compile and run it using:

~~~~ {.shell} $ ghc –make BitAdd.hs [1 of 1] Compiling Main ( BitAdd.hs, BitAdd.o ) Linking BitAdd …

$ ./BitAdd Depth 0: Completed 2 test(s) without failure. Depth 1: Completed 6 test(s) without failure. Depth 2: Completed 14 test(s) without failure. Depth 3: Completed 30 test(s) without failure. ~~~~