{-# LANGUAGE CPP #-}
#ifndef NO_SAFE_HASKELL
{-# LANGUAGE Trustworthy #-}
#endif
#ifndef NO_MULTI_PARAM_TYPE_CLASSES
{-# LANGUAGE MultiParamTypeClasses #-}
#endif
#ifndef NO_NEWTYPE_DERIVING
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
#endif
-- | Modifiers for test data.
--
-- These types do things such as restricting the kind of test data that can be generated.
-- They can be pattern-matched on in properties as a stylistic
-- alternative to using explicit quantification.
--
-- Examples:
--
-- @
-- -- Functions cannot be shown (but see "Test.QuickCheck.Function")
-- prop_TakeDropWhile ('Blind' p) (xs :: ['A']) =
-- takeWhile p xs ++ dropWhile p xs == xs
-- @
--
-- @
-- prop_TakeDrop ('NonNegative' n) (xs :: ['A']) =
-- take n xs ++ drop n xs == xs
-- @
--
-- @
-- -- cycle does not work for empty lists
-- prop_Cycle ('NonNegative' n) ('NonEmpty' (xs :: ['A'])) =
-- take n (cycle xs) == take n (xs ++ cycle xs)
-- @
--
-- @
-- -- Instead of 'forAll' 'orderedList'
-- prop_Sort ('Ordered' (xs :: ['OrdA'])) =
-- sort xs == xs
-- @
module Test.QuickCheck.Modifiers
(
-- ** Type-level modifiers for changing generator behavior
Blind(..)
, Fixed(..)
, OrderedList(..)
, NonEmptyList(..)
, Positive(..)
, NonZero(..)
, NonNegative(..)
, Large(..)
, Small(..)
, Smart(..)
, Shrink2(..)
#ifndef NO_MULTI_PARAM_TYPE_CLASSES
, Shrinking(..)
, ShrinkState(..)
#endif
, ASCIIString(..)
, UnicodeString(..)
, PrintableString(..)
)
where
--------------------------------------------------------------------------
-- imports
import Test.QuickCheck.Gen
import Test.QuickCheck.Arbitrary
import Data.List
( sort
)
import Data.Ix (Ix)
--------------------------------------------------------------------------
-- | @Blind x@: as x, but x does not have to be in the 'Show' class.
newtype Blind a = Blind {getBlind :: a}
deriving ( Eq, Ord
#ifndef NO_NEWTYPE_DERIVING
, Num, Integral, Real, Enum
#endif
)
instance Functor Blind where
fmap f (Blind x) = Blind (f x)
instance Show (Blind a) where
show _ = "(*)"
instance Arbitrary a => Arbitrary (Blind a) where
arbitrary = Blind `fmap` arbitrary
shrink (Blind x) = [ Blind x' | x' <- shrink x ]
--------------------------------------------------------------------------
-- | @Fixed x@: as x, but will not be shrunk.
newtype Fixed a = Fixed {getFixed :: a}
deriving ( Eq, Ord, Show, Read
#ifndef NO_NEWTYPE_DERIVING
, Num, Integral, Real, Enum
#endif
)
instance Functor Fixed where
fmap f (Fixed x) = Fixed (f x)
instance Arbitrary a => Arbitrary (Fixed a) where
arbitrary = Fixed `fmap` arbitrary
-- no shrink function
--------------------------------------------------------------------------
-- | @Ordered xs@: guarantees that xs is ordered.
newtype OrderedList a = Ordered {getOrdered :: [a]}
deriving ( Eq, Ord, Show, Read )
instance Functor OrderedList where
fmap f (Ordered x) = Ordered (map f x)
instance (Ord a, Arbitrary a) => Arbitrary (OrderedList a) where
arbitrary = Ordered `fmap` orderedList
shrink (Ordered xs) =
[ Ordered xs'
| xs' <- shrink xs
, sort xs' == xs'
]
--------------------------------------------------------------------------
-- | @NonEmpty xs@: guarantees that xs is non-empty.
newtype NonEmptyList a = NonEmpty {getNonEmpty :: [a]}
deriving ( Eq, Ord, Show, Read )
instance Functor NonEmptyList where
fmap f (NonEmpty x) = NonEmpty (map f x)
instance Arbitrary a => Arbitrary (NonEmptyList a) where
arbitrary = NonEmpty `fmap` (arbitrary `suchThat` (not . null))
shrink (NonEmpty xs) =
[ NonEmpty xs'
| xs' <- shrink xs
, not (null xs')
]
--------------------------------------------------------------------------
-- | @Positive x@: guarantees that @x \> 0@.
newtype Positive a = Positive {getPositive :: a}
deriving ( Eq, Ord, Show, Read
#ifndef NO_NEWTYPE_DERIVING
, Enum
#endif
)
instance Functor Positive where
fmap f (Positive x) = Positive (f x)
instance (Num a, Ord a, Arbitrary a) => Arbitrary (Positive a) where
arbitrary =
((Positive . abs) `fmap` (arbitrary `suchThat` (/= 0))) `suchThat` gt0
where gt0 (Positive x) = x > 0
shrink (Positive x) =
[ Positive x'
| x' <- shrink x
, x' > 0
]
--------------------------------------------------------------------------
-- | @NonZero x@: guarantees that @x \/= 0@.
newtype NonZero a = NonZero {getNonZero :: a}
deriving ( Eq, Ord, Show, Read
#ifndef NO_NEWTYPE_DERIVING
, Enum
#endif
)
instance Functor NonZero where
fmap f (NonZero x) = NonZero (f x)
instance (Num a, Eq a, Arbitrary a) => Arbitrary (NonZero a) where
arbitrary = fmap NonZero $ arbitrary `suchThat` (/= 0)
shrink (NonZero x) = [ NonZero x' | x' <- shrink x, x' /= 0 ]
--------------------------------------------------------------------------
-- | @NonNegative x@: guarantees that @x \>= 0@.
newtype NonNegative a = NonNegative {getNonNegative :: a}
deriving ( Eq, Ord, Show, Read
#ifndef NO_NEWTYPE_DERIVING
, Enum
#endif
)
instance Functor NonNegative where
fmap f (NonNegative x) = NonNegative (f x)
instance (Num a, Ord a, Arbitrary a) => Arbitrary (NonNegative a) where
arbitrary =
(frequency
-- why is this distrbution like this?
[ (5, (NonNegative . abs) `fmap` arbitrary)
, (1, return (NonNegative 0))
]
) `suchThat` ge0
where ge0 (NonNegative x) = x >= 0
shrink (NonNegative x) =
[ NonNegative x'
| x' <- shrink x
, x' >= 0
]
--------------------------------------------------------------------------
-- | @Large x@: by default, QuickCheck generates 'Int's drawn from a small
-- range. @Large Int@ gives you values drawn from the entire range instead.
newtype Large a = Large {getLarge :: a}
deriving ( Eq, Ord, Show, Read
#ifndef NO_NEWTYPE_DERIVING
, Num, Integral, Real, Enum, Ix
#endif
)
instance Functor Large where
fmap f (Large x) = Large (f x)
instance (Integral a, Bounded a) => Arbitrary (Large a) where
arbitrary = fmap Large arbitrarySizedBoundedIntegral
shrink (Large x) = fmap Large (shrinkIntegral x)
--------------------------------------------------------------------------
-- | @Small x@: generates values of @x@ drawn from a small range.
-- The opposite of 'Large'.
newtype Small a = Small {getSmall :: a}
deriving ( Eq, Ord, Show, Read
#ifndef NO_NEWTYPE_DERIVING
, Num, Integral, Real, Enum, Ix
#endif
)
instance Functor Small where
fmap f (Small x) = Small (f x)
instance Integral a => Arbitrary (Small a) where
arbitrary = fmap Small arbitrarySizedIntegral
shrink (Small x) = map Small (shrinkIntegral x)
--------------------------------------------------------------------------
-- | @Shrink2 x@: allows 2 shrinking steps at the same time when shrinking x
newtype Shrink2 a = Shrink2 {getShrink2 :: a}
deriving ( Eq, Ord, Show, Read
#ifndef NO_NEWTYPE_DERIVING
, Num, Integral, Real, Enum
#endif
)
instance Functor Shrink2 where
fmap f (Shrink2 x) = Shrink2 (f x)
instance Arbitrary a => Arbitrary (Shrink2 a) where
arbitrary =
Shrink2 `fmap` arbitrary
shrink (Shrink2 x) =
[ Shrink2 y | y <- shrink_x ] ++
[ Shrink2 z
| y <- shrink_x
, z <- shrink y
]
where
shrink_x = shrink x
--------------------------------------------------------------------------
-- | @Smart _ x@: tries a different order when shrinking.
data Smart a =
Smart Int a
instance Functor Smart where
fmap f (Smart n x) = Smart n (f x)
instance Show a => Show (Smart a) where
showsPrec n (Smart _ x) = showsPrec n x
instance Arbitrary a => Arbitrary (Smart a) where
arbitrary =
do x <- arbitrary
return (Smart 0 x)
shrink (Smart i x) = take i' ys `ilv` drop i' ys
where
ys = [ Smart j y | (j,y) <- [0..] `zip` shrink x ]
i' = 0 `max` (i-2)
[] `ilv` bs = bs
as `ilv` [] = as
(a:as) `ilv` (b:bs) = a : b : (as `ilv` bs)
{-
shrink (Smart i x) = part0 ++ part2 ++ part1
where
ys = [ Smart i y | (i,y) <- [0..] `zip` shrink x ]
i' = 0 `max` (i-2)
k = i `div` 10
part0 = take k ys
part1 = take (i'-k) (drop k ys)
part2 = drop i' ys
-}
-- drop a (drop b xs) == drop (a+b) xs | a,b >= 0
-- take a (take b xs) == take (a `min` b) xs
-- take a xs ++ drop a xs == xs
-- take k ys ++ take (i'-k) (drop k ys) ++ drop i' ys
-- == take k ys ++ take (i'-k) (drop k ys) ++ drop (i'-k) (drop k ys)
-- == take k ys ++ take (i'-k) (drop k ys) ++ drop (i'-k) (drop k ys)
-- == take k ys ++ drop k ys
-- == ys
#ifndef NO_MULTI_PARAM_TYPE_CLASSES
--------------------------------------------------------------------------
-- | @Shrinking _ x@: allows for maintaining a state during shrinking.
data Shrinking s a =
Shrinking s a
class ShrinkState s a where
shrinkInit :: a -> s
shrinkState :: a -> s -> [(a,s)]
instance Functor (Shrinking s) where
fmap f (Shrinking s x) = Shrinking s (f x)
instance Show a => Show (Shrinking s a) where
showsPrec n (Shrinking _ x) = showsPrec n x
instance (Arbitrary a, ShrinkState s a) => Arbitrary (Shrinking s a) where
arbitrary =
do x <- arbitrary
return (Shrinking (shrinkInit x) x)
shrink (Shrinking s x) =
[ Shrinking s' x'
| (x',s') <- shrinkState x s
]
#endif /* NO_MULTI_PARAM_TYPE_CLASSES */
--------------------------------------------------------------------------
-- | @ASCIIString@: generates an ASCII string.
newtype ASCIIString = ASCIIString {getASCIIString :: String}
deriving ( Eq, Ord, Show, Read )
instance Arbitrary ASCIIString where
arbitrary = ASCIIString `fmap` listOf arbitraryASCIIChar
shrink (ASCIIString xs) = ASCIIString `fmap` shrink xs
--------------------------------------------------------------------------
-- | @UnicodeString@: generates a unicode String.
-- The string will not contain surrogate pairs.
newtype UnicodeString = UnicodeString {getUnicodeString :: String}
deriving ( Eq, Ord, Show, Read )
instance Arbitrary UnicodeString where
arbitrary = UnicodeString `fmap` listOf arbitraryUnicodeChar
shrink (UnicodeString xs) = UnicodeString `fmap` shrink xs
--------------------------------------------------------------------------
-- | @PrintableString@: generates a printable unicode String.
-- The string will not contain surrogate pairs.
newtype PrintableString = PrintableString {getPrintableString :: String}
deriving ( Eq, Ord, Show, Read )
instance Arbitrary PrintableString where
arbitrary = PrintableString `fmap` listOf arbitraryPrintableChar
shrink (PrintableString xs) = PrintableString `fmap` shrink xs
-- the end.