Test for trying to read negative length with getByteString.

If not checking the requested read length, we're most likely to
segfault.

BitsQC.hs

@@ -14,6 +14,7 @@ import Data.Binary.Bits.Get
 import Data.Binary.Bits.Put
 
 import qualified Data.ByteString as B
+import qualified Data.ByteString.Lazy as L
 
 import Control.Applicative
 import Data.Bits
@@ -39,6 +40,9 @@ tests =
   , testGroup "Custom test cases"
       [ testProperty "prop_composite_case" prop_composite_case ]
 
+  , testGroup "getByteString"
+      [ testProperty "prop_getByteString_negative" prop_getByteString_negative ]
+
   , testGroup "prop_bitput_with_get_from_binary"
       [ testProperty "Word8"  (prop_bitput_with_get_from_binary :: W [Word8]  -> Property)
       , testProperty "Word16" (prop_bitput_with_get_from_binary :: W [Word16] -> Property)
@@ -103,6 +107,12 @@ tests =
       ]
   ]
 
+
+prop_getByteString_negative :: Int -> Property
+prop_getByteString_negative n =
+  n < 1 ==>
+    runGet (runBitGet (getByteString n)) L.empty == B.empty
+
 prop_putget_with_bitreq :: (BinaryBit a, Num a, Bits a, Ord a) => W a -> Property
 prop_putget_with_bitreq (W w) = property $
   -- write all words with as many bits as it's required