diff --git a/tests/KAT_AFIS.hs b/tests/KAT_AFIS.hs
index c3bcc4d..f4cb9b5 100644
--- a/tests/KAT_AFIS.hs
+++ b/tests/KAT_AFIS.hs
@@ -33,8 +33,7 @@ instance Show AFISParams where
     show (AFISParams dat expand _ _) = "data: " ++ show dat ++ " expanded: " ++ show expand
 
 instance Arbitrary AFISParams where
-    arbitrary = AFISParams <$> arbitraryBS <*> choose (2,2) <*> elements [SHA1] <*> arbitrary
-      where arbitraryBS = choose (3,46) >>= \sz -> B.pack <$> replicateM sz arbitrary 
+    arbitrary = AFISParams <$> arbitraryBSof 3 46 <*> choose (2,2) <*> elements [SHA1] <*> arbitrary
 
 instance Arbitrary ChaChaDRG where
     arbitrary = drgNewTest <$> arbitrary
diff --git a/tests/KAT_HMAC.hs b/tests/KAT_HMAC.hs
index 65ef6a4..a416ac8 100644
--- a/tests/KAT_HMAC.hs
+++ b/tests/KAT_HMAC.hs
@@ -6,7 +6,6 @@ import Crypto.Hash (MD5(..), SHA1(..), SHA256(..)
                    , Kekkak_224(..), Kekkak_256(..), Kekkak_384(..), Kekkak_512(..)
                    , SHA3_224(..), SHA3_256(..), SHA3_384(..), SHA3_512(..)
                    , HashAlgorithm, digestFromByteString)
---import Data.Foldable (foldl')
 import qualified Data.ByteString as B
 
 import Imports
@@ -116,12 +115,10 @@ macTests =
 data MacIncremental a = MacIncremental ByteString ByteString (HMAC.HMAC a)
     deriving (Show,Eq)
 
-arbitraryBS = B.pack <$> (choose (1,299) >>= \i -> replicateM i arbitrary)
-
 instance HashAlgorithm a => Arbitrary (MacIncremental a) where
     arbitrary = do
-        key <- B.pack <$> replicateM 65 (choose (0x30,0x30)) -- B.pack arbitraryBS
-        msg <- B.pack <$> replicateM 2 (choose (0x40,0x40)) -- B.pack arbitraryBS
+        key <- arbitraryBSof 1 89
+        msg <- arbitraryBSof 1 99
         return $ MacIncremental key msg (HMAC.hmac key msg)
 
 data MacIncrementalList a = MacIncrementalList ByteString [ByteString] (HMAC.HMAC a)
@@ -129,11 +126,9 @@ data MacIncrementalList a = MacIncrementalList ByteString [ByteString] (HMAC.HMA
 
 instance HashAlgorithm a => Arbitrary (MacIncrementalList a) where
     arbitrary = do
-        --key  <- arbitraryBS
-        --msgs <- choose (1,20) >>= \i -> replicateM i arbitraryBS
-        key  <- B.pack <$> replicateM 128 (choose (0x30,0x30)) -- B.pack arbitraryBS
-        msgs <- B.pack <$> replicateM 2 (choose (0x40,0x40)) -- B.pack arbitraryBS
-        return $ MacIncrementalList key [msgs] (HMAC.hmac key (B.concat [msgs]))
+        key  <- arbitraryBSof 1 89
+        msgs <- choose (1,20) >>= \n -> replicateM n (arbitraryBSof 1 99)
+        return $ MacIncrementalList key msgs (HMAC.hmac key (B.concat msgs))
 
 macIncrementalTests :: [TestTree]
 macIncrementalTests =
diff --git a/tests/Utils.hs b/tests/Utils.hs
index a457f3d..0d30877 100644
--- a/tests/Utils.hs
+++ b/tests/Utils.hs
@@ -14,6 +14,12 @@ newtype ChunkingLen = ChunkingLen [Int]
 instance Arbitrary ChunkingLen where
     arbitrary = ChunkingLen `fmap` replicateM 16 (choose (0,14))
 
+arbitraryBS :: Int -> Gen ByteString
+arbitraryBS n = B.pack `fmap` replicateM n arbitrary
+
+arbitraryBSof :: Int -> Int -> Gen ByteString
+arbitraryBSof minSize maxSize = choose (minSize, maxSize) >>= \n -> (B.pack `fmap` replicateM n arbitrary)
+
 chunkS :: ChunkingLen -> ByteString -> [ByteString]
 chunkS (ChunkingLen originalChunks) = loop originalChunks
   where loop l bs