QuickCheck is a Haskell library for software testing. It generates test cases and validates them against assertions provided by the programmer.
Questions tagged [quickcheck]
422 questions
7
votes
1 answer
How do I improve QuickCheck and Parsec debugging?
I am using Haskell and Parsec to parse a file format. My parsing function looks something like:
parseInput :: String -> Model
parseInput input = ...
data Model = Model { mNumV :: Int, mNumF :: Int, ... }
In order to test this, I am using…
sdasdadas
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7
votes
1 answer
Haskell quickcheck to generate and test rose trees?
I am trying out a simple rose tree code.
data RoseT a = Leaf a | Node a [RoseT a] deriving (Show)
instance Eq (RoseT a) where
(==) (Leaf a) (Leaf b) = a == b
(==) (Node a rs1) (Node b rs2) = and ((a==b): (zipWith (==) rs1 rs2))
(==) _ _ = False…
Tem Pora
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6
votes
3 answers
Why is this implementation a bad instance of the Foldable Typeclass?
I'm working through the wonderful Haskell Book. At the end of the Traversable chapter (21), I need to write an instance for the following Tree:
data Tree a =
Empty
| Leaf a
| Node (Tree a) a (Tree a)
Here is a link to the full code of my…
javinor
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- 8
6
votes
1 answer
Make Test.QuickCheck.Batch use a default type for testing list functions
I am testing a function called extractions that operates over any list.
extractions :: [a] -> [(a,[a])]
extractions [] = []
extractions l = extract l []
where extract [] _ = []
extract (x:xs) prev = (x, prev++xs) : extract xs (x :…
Nathan Shively-Sanders
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- 4
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6
votes
1 answer
Generate injective functions with QuickCheck?
I'm using QuickCheck to generate arbitrary functions, and I'd like to generate arbitrary injective functions (i.e. f a == f b if and only if a == b).
I thought I had it figured out:
newtype Injective = Injective (Fun Word Char) deriving…
ivan
- 6,032
- 9
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- 65
6
votes
2 answers
QuickCheck: why isn't there a function to pass a test and what to use instead?
Why isn't there a QuickCheck function similar to hedgehog's success? In particular I was wondering how one could translate a property like the following one:
prop_specialPair :: Property
prop_specialPair = property $ do
(_, xs) <- forAll…
Damian Nadales
- 4,907
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6
votes
1 answer
Why does shrinking stop once one of the terms is fully shrunk
I'm looking at the comments in shrink:
It is tempting to write the last line as [Branch x' l' r' | x' <- shrink x, l' <- shrink l, r' <- shrink r] but this is the wrong thing! It will force QuickCheck to shrink x, l and r in tandem, and shrinking…
Damian Nadales
- 4,907
- 1
- 21
- 34
6
votes
1 answer
CoArbitrary in Haskell
I am working through the Haskell Book and have come to the point of writing an Arbitrary instance for newType Comp. The code is below
instance Show (Comp a) where
show f = "Unicorns!!"
newtype Comp a =
Comp { unComp :: (a -> a) }
instance…
tesserakt
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- 4
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6
votes
0 answers
How to test the Functor laws with the checkers library
How do I use the checkers library to test the Functor laws of a simple Parser?
import Test.QuickCheck
import Test.QuickCheck.Checkers
import Test.QuickCheck.Classes
import qualified Data.ByteString as BS
type Index = Int
newtype Parser a = Parser…
Jogger
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6
votes
1 answer
Complete minimal example for using quickCheckAll
I could use a complete example of how to use quickCheckAll. Here's what I've tried so far:
In a file A.hs:
module A where
import Test.QuickCheck
prop_a = 1 == 0
check = do
return []
$quickCheckAll
In another file…
Guillaume Chérel
- 1,478
- 8
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6
votes
1 answer
fscheck doesn't generate random enough data
I'm playing with FsCheck so I have this implementation:
let add a b =
if a > 100
then failwith "nasty bug"
else a + b
...and this FsCheck based test:
fun (a:int) -> (add a 0) = a
|> Check.QuickThrowOnFailure
and the test never fails.…
vidi
- 2,056
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- 34
6
votes
3 answers
How to use QuickCheck to test database related functions?
I need to test a lot of functions that access the database (via Persistent). While I can do this using monadicIO and withSqlitePool it will result in inefficient tests. Each test, not property, but test, will create and destroy the DB pool. How do I…
Saurabh Nanda
- 6,373
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6
votes
1 answer
Is it possible to check cases when exception is thrown with QuickCheck?
Suppose I have a function that should calculate some value in one case and
throw an exception otherwise. I would like to use QuickCheck to ensure my
function behaves correctly, however is not obvious how to perform this sort
of check. Is it possible…
Mark Karpov
- 7,499
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6
votes
1 answer
Generate Strings from Grammar in ScalaCheck
In Scala, I have a grammar implemented using the Parser Combinators library. Now, what I want to do is generate random strings given a grammar from the parser combinators library.
It seems to me, that what the ScalaCheck library does it somehow the…
Felix
- 8,385
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6
votes
1 answer
QuickCheck: How to combine two generators?
I have two generators, gen_n & gen_arr:
gen_n :: Gen Int
gen_n = suchThat arbitrary (\i -> i >= 0 && i <= 10)
gen_elem :: Gen Int
gen_elem = suchThat arbitrary (\i -> i >= 0 && i <= 100)
gen_arr :: Gen [Int]
gen_arr = listOf gen_elem
How can I…
muhuk
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