diff --git a/gray-extended.cabal b/gray-extended.cabal
--- a/gray-extended.cabal
+++ b/gray-extended.cabal
@@ -1,5 +1,5 @@
 name:           gray-extended
-version:        1.5
+version:        1.5.1
 synopsis:       Gray encoding schemes
 description:    Gray codes satisfy the property that two successive values 
                 differ in only one digit. Usually the term \"Gray code\"
@@ -16,6 +16,15 @@
 maintainer:     amy@nualeargais.ie
 license-file:   LICENSE
 
+source-repository head
+  type:     git
+  location: https://github.com/mhwombat/gray-extended.git
+
+source-repository this
+  type:     git
+  location: https://github.com/mhwombat/gray-extended.git
+  tag:      1.5.1
+
 library
   hs-source-dirs:  src
   build-depends:   base ==4.*
@@ -26,10 +35,10 @@
   type:            exitcode-stdio-1.0
   build-depends:   base ==4.*,
                    test-framework-quickcheck2 == 0.3.*,
-                   QuickCheck == 2.4.*,
-                   test-framework == 0.*,
+                   QuickCheck == 2.7.*,
+                   test-framework == 0.8.*,
                    gray-extended
   hs-source-dirs:  test
   ghc-options:     -Wall -Werror -rtsopts
   main-is:         Main.hs
-
+  other-modules:   Codec.GrayQC
diff --git a/test/Codec/GrayQC.hs b/test/Codec/GrayQC.hs
new file mode 100644
--- /dev/null
+++ b/test/Codec/GrayQC.hs
@@ -0,0 +1,85 @@
+module Codec.GrayQC
+  (
+    test
+  ) where
+
+import Codec.Gray
+import Data.List (nub)
+import Data.Word (Word8)
+import Test.Framework as TF (Test, testGroup)
+import Test.Framework.Providers.QuickCheck2 (testProperty)
+import Test.QuickCheck ((==>), Property, Gen, Arbitrary, arbitrary, choose, 
+  property, sized)
+
+prop_successive_values_differ_in_one_place1 :: Int -> Property
+prop_successive_values_differ_in_one_place1 k = k > 0 ==>
+  nub (diffCounts xs) == [1]
+    where xs = grayCodes k'
+          k' = min 10 k -- avoid long tests
+
+data TestParms = TestParms String Int deriving Show
+
+sizedTestParms :: Int -> Gen TestParms
+sizedTestParms n = do
+  let n' = 2 + (min 8 n) -- keep number of digits and bits low to speed up tests
+  let digits = take n' ['a' .. 'z']
+  k <- choose (1,min 4 (n+1))
+  return $ TestParms digits k
+
+instance Arbitrary TestParms where
+  arbitrary = sized sizedTestParms
+  
+prop_successive_values_differ_in_one_place2 :: TestParms -> Property
+prop_successive_values_differ_in_one_place2 (TestParms ds k) = property $
+  nub (diffCounts xs) == [1]
+    where xs = naryGrayCodes ds k
+
+diffCounts :: Eq b => [[b]] -> [Int]
+diffCounts [] = []
+diffCounts [_] = []
+diffCounts (x1:x2:xs) = (diffCount x1 x2) : diffCounts (x2:xs)
+
+diffCount :: Eq b => [b] -> [b] -> Int
+diffCount as bs = length $ filter (\x -> x) $ zipWith (/=) as bs
+
+prop_encoding_round_trippable :: Int -> Property
+prop_encoding_round_trippable n =
+  n >= 0 ==> (grayToIntegral . integralToGray $ n) == n
+
+prop_decoding_round_trippable :: Int -> Property
+prop_decoding_round_trippable n =
+  n >= 0 ==> (integralToGray . grayToIntegral $ n) == n
+
+prop_integralToGray_same_as_encode :: Word8 -> Property
+prop_integralToGray_same_as_encode n =
+  property $ integralToGray n == boolsToIntegral bits
+    where bits = (grayCodes 8) !! (fromIntegral n)
+
+boolsToIntegral :: Num c => [Bool] -> c
+boolsToIntegral bs = f 0 1 . reverse $ bs
+  where f total _ [] = total
+        f total factor (b:bs') = f total' (factor*2) bs'
+          where total' = if b then total + factor else total
+                
+-- integralToBools :: (Integral a, Bits a) => a -> [Bool]
+-- integralToBools 0 = []
+-- integralToBools n = integralToBools (n `shiftR` 1) ++ [f (n `mod` 2)]
+--   where f 0 = False
+--         f 1 = True
+
+test :: Test
+test = testGroup "Codec.GrayQC"
+  [
+    testProperty "prop_successive_values_differ_in_one_place1"
+      prop_successive_values_differ_in_one_place1,
+    testProperty "prop_successive_values_differ_in_one_place2"
+      prop_successive_values_differ_in_one_place2,
+    testProperty "prop_encoding_round_trippable"
+      prop_encoding_round_trippable,
+    testProperty "prop_decoding_round_trippable"
+      prop_decoding_round_trippable,
+    testProperty "prop_integralToGray_same_as_encode"
+      prop_integralToGray_same_as_encode
+  ]
+
+