diff --git a/src/Crypto/RNCryptor/Types.hs b/src/Crypto/RNCryptor/Types.hs
index 7e21eac..c1ddef4 100644
--- a/src/Crypto/RNCryptor/Types.hs
+++ b/src/Crypto/RNCryptor/Types.hs
@@ -2,6 +2,7 @@
 module Crypto.RNCryptor.Types 
      ( RNCryptorHeader(..)
      , RNCryptorContext(ctxHeader, ctxCipher)
+     , UserInput(..)
      , newRNCryptorContext
      , newRNCryptorHeader
      , renderRNCryptorHeader
@@ -17,6 +18,7 @@ import Control.Applicative
 import Control.Monad
 import Crypto.Cipher.AES
 import Crypto.PBKDF.ByteString
+import Test.QuickCheck
 
 
 data RNCryptorHeader = RNCryptorHeader {
@@ -36,6 +38,25 @@ data RNCryptorHeader = RNCryptorHeader {
       -- as the HMAC is at the end of the file.
       }
 
+instance Show RNCryptorHeader where
+  show = C8.unpack . renderRNCryptorHeader
+
+instance Arbitrary RNCryptorHeader where
+  arbitrary = do
+    let version = toEnum 3
+    let options = toEnum 1
+    eSalt    <- C8.pack <$> vector saltSize
+    iv       <- C8.pack <$> vector blockSize
+    hmacSalt <- C8.pack <$> vector saltSize
+    return RNCryptorHeader {
+          rncVersion = version
+        , rncOptions = options
+        , rncEncryptionSalt = eSalt
+        , rncHMACSalt = hmacSalt
+        , rncIV = iv
+        , rncHMAC = \uKey -> sha1PBKDF2 uKey hmacSalt 10000 32
+        }
+
 --------------------------------------------------------------------------------
 saltSize :: Int
 saltSize = 8
@@ -82,6 +103,11 @@ data RNCryptorContext = RNCryptorContext {
       , ctxCipher :: AES
       }
 
+newtype UserInput = UI { unInput :: ByteString } deriving Show
+
+instance Arbitrary UserInput where
+  arbitrary = UI . C8.pack <$> arbitrary
+
 --------------------------------------------------------------------------------
 newRNCryptorContext :: ByteString -> RNCryptorHeader -> RNCryptorContext
 newRNCryptorContext userKey hdr =
diff --git a/src/Crypto/RNCryptor/V3.hs b/src/Crypto/RNCryptor/V3.hs
index a4a2e2d..69f33c4 100644
--- a/src/Crypto/RNCryptor/V3.hs
+++ b/src/Crypto/RNCryptor/V3.hs
@@ -2,7 +2,9 @@
 module Crypto.RNCryptor.V3 (
     module Crypto.RNCryptor.V3.Encrypt
   , module Crypto.RNCryptor.V3.Decrypt
+  , module Crypto.RNCryptor.Types
   ) where
 
 import Crypto.RNCryptor.V3.Encrypt
 import Crypto.RNCryptor.V3.Decrypt
+import Crypto.RNCryptor.Types
diff --git a/test/Main.hs b/test/Main.hs
index 09e12b5..a5e17f1 100644
--- a/test/Main.hs
+++ b/test/Main.hs
@@ -1,11 +1,8 @@
 {-# LANGUAGE OverloadedStrings #-}
 module Main where
 
-import           System.Environment
-import           Data.Monoid
 import           Tests
 import           Test.Tasty
-import           Test.Tasty.HUnit
 import           Test.Tasty.QuickCheck
 
 ----------------------------------------------------------------------
@@ -18,5 +15,7 @@ main :: IO ()
 main = do
   defaultMainWithIngredients defaultIngredients $
     testGroup "RNCryptor tests" $ [
-         testGroup "RNCryptor properties" []
+         withQuickCheckDepth "RNCryptor properties" 100 [
+           testProperty "encrypt/decrypt roundtrip" testEncryptDecryptRoundtrip
+         ]
      ]
diff --git a/test/Tests.hs b/test/Tests.hs
index 8c4d87e..17c80fb 100644
--- a/test/Tests.hs
+++ b/test/Tests.hs
@@ -1,3 +1,23 @@
+{-# LANGUAGE ScopedTypeVariables #-}
 module Tests where
 
-import Test.Tasty.HUnit
+import Test.Tasty.QuickCheck
+import Crypto.RNCryptor.V3
+import Control.Applicative
+import qualified Data.ByteString as B
+
+
+newtype TestVector = TV (UserInput, UserInput, RNCryptorHeader) deriving Show
+
+instance Arbitrary TestVector where
+  arbitrary = TV <$> ((,,) <$> arbitrary <*> arbitrary <*> arbitrary)
+
+
+testEncryptDecryptRoundtrip :: Property
+testEncryptDecryptRoundtrip =
+  forAll arbitrary $ \(TV (input,pwd,hdr)) ->
+    B.length (unInput input) > 0 &&
+    B.length (unInput pwd) > 0 ==>
+    let ctx = newRNCryptorContext (unInput pwd) hdr
+        encrypted = encrypt ctx (unInput input)
+    in decrypt encrypted (unInput pwd) == unInput input
diff --git "a/\177" "b/\177"
new file mode 100644
index 0000000..e69de29