add resize tests

Author: safareli

test/Main.purs

@@ -6,16 +6,19 @@ import Control.Monad.Eff (Eff)
 import Control.Monad.Eff.Console (CONSOLE, log, logShow)
 import Control.Monad.Eff.Exception (try, EXCEPTION)
 import Control.Monad.Eff.Random (RANDOM)
+import Control.Monad.Gen.Class as MGen
 import Data.Array.Partial (head)
 import Data.Either (isLeft)
 import Data.Foldable (sum)
 import Data.Generic.Rep (class Generic)
 import Data.Generic.Rep.Show (genericShow)
+import Data.Tuple (fst)
 import Partial.Unsafe (unsafePartial)
 import Test.Assert (assert, ASSERT)
 import Test.QuickCheck (class Testable, quickCheck, (/=?), (<=?), (<?), (==?), (>=?), (>?))
 import Test.QuickCheck.Arbitrary (arbitrary, genericArbitrary, class Arbitrary)
-import Test.QuickCheck.Gen (Gen, vectorOf, randomSample')
+import Test.QuickCheck.Gen (Gen, vectorOf, randomSample', resize, Size, runGen, sized)
+import Test.QuickCheck.LCG (mkSeed)
 
 data Foo a = F0 a | F1 a a | F2 { foo :: a, bar :: Array a }
 derive instance genericFoo :: Generic (Foo a) _
@@ -31,8 +34,26 @@ quickCheckFail
 quickCheckFail = assert <=< map isLeft <<< try <<< quickCheck
 
 
+testResize :: (forall a. Size -> Gen a -> Gen a) -> Boolean
+testResize resize' =
+  let
+    initialSize = 2
+    gen = do
+      s1 <- sized pure
+      s2 <- resize' 1 (sized pure)
+      s3 <- sized pure
+      pure $ [ s1, s2, s3 ] == [ initialSize, 1, initialSize ]
+  in
+    fst $ runGen gen { newSeed: mkSeed 0, size: initialSize }
+
+
 main :: Eff (assert :: ASSERT, console :: CONSOLE, random :: RANDOM, exception :: EXCEPTION) Unit
 main = do
+  log "MonadGen.resize"
+  assert (testResize (MGen.resize <<< const))
+  log "Gen.resize"
+  assert (testResize (resize))
+
   log "Try with some little Gens first"
   logShow =<< go 10
   logShow =<< go 100