diff --git a/Data/Digest/CityHash.hs b/Data/Digest/CityHash.hs
--- a/Data/Digest/CityHash.hs
+++ b/Data/Digest/CityHash.hs
@@ -14,9 +14,9 @@
 -- and 128-bit interfaces.
 -- 
 -- Note that CityHash is designed to work on architectures where
--- unaligned reads have a small penalty. In practice it is only used
--- at Google on little-endian Intel/AMD CPUs it seems, and has not
--- been tested on big-endian architectures.
+-- unaligned reads do not have a large penalty. In practice it is only
+-- used at Google on little-endian Intel/AMD CPUs it seems, and has
+-- not been tested on big-endian architectures.
 -- 
 module Data.Digest.CityHash
 ( -- * Hashing values 
diff --git a/cityhash.cabal b/cityhash.cabal
--- a/cityhash.cabal
+++ b/cityhash.cabal
@@ -1,5 +1,5 @@
 name:                cityhash
-version:             0.0.1
+version:             0.0.2
 synopsis:            bindings to Google CityHash
 description:
   This package implements a binding to the google CityHash family of hashing functions.
@@ -17,7 +17,7 @@
 extra-source-files:
   cbits/city.cc, cbits/city.h,
   cbits/hs_city.cc, cbits/hs_city.h,
-  README.md
+  README.md, tests/Properties.hs
 
 source-repository head
   type: git
@@ -34,4 +34,20 @@
   extra-libraries: stdc++
 
   ghc-options:      -Wall -O2 -fwarn-tabs
+  default-language: Haskell98
+
+test-suite properties
+  hs-source-dirs: tests
+  main-is:        Properties.hs
+  type:           exitcode-stdio-1.0
+
+  build-depends:
+    base    >= 3 && < 5,
+    bytestring     == 0.9.*,
+    QuickCheck     == 2.4.*,
+    test-framework == 0.3.*,
+    test-framework-quickcheck2 == 0.2.*,
+    cityhash
+
+  ghc-options:      -fno-cse
   default-language: Haskell98
diff --git a/tests/Properties.hs b/tests/Properties.hs
new file mode 100644
--- /dev/null
+++ b/tests/Properties.hs
@@ -0,0 +1,21 @@
+{-# LANGUAGE ViewPatterns #-}
+module Main (main) where
+
+import qualified Data.ByteString as S
+import Data.Digest.CityHash
+
+import Test.Framework (defaultMain, testGroup)
+import Test.Framework.Providers.QuickCheck2 (testProperty)
+
+main :: IO ()
+main = defaultMain [ testGroup "simple" [
+                       testProperty "cityhash64 is pure" prop_city64_pure
+                     , testProperty "cityhash128 is pure" prop_city128_pure
+                     ]
+                   ]
+
+prop_city64_pure (S.pack -> xs)
+  = cityHash64 xs == cityHash64 xs
+
+prop_city128_pure (S.pack -> xs)
+  = cityHash128 xs == cityHash128 xs