diff --git a/tests/GenerateRegressionTests.hs b/tests/GenerateRegressionTests.hs
new file mode 100644
index 0000000..80c35ba
--- /dev/null
+++ b/tests/GenerateRegressionTests.hs
@@ -0,0 +1,40 @@
+{-# LANGUAGE NoMonomorphismRestriction #-}
+import Control.Monad
+import Data.ByteString (pack)
+import Data.Encoding
+import System.Random
+
+-- for example:
+import Data.Encoding.ISO2022JP
+main = generate ISO2022JP
+-- end example
+
+randomRepeat f max = randomRIO (0, max) >>= flip replicateM f
+randomString = randomRepeat randomIO
+randomGoodString = randomRepeat . randomGoodChar
+randomGoodChar f = let
+	good = filter f [minBound..maxBound]
+	n    = length good
+	in do
+	i <- randomRIO (0, n-1)
+	return (good !! i)
+
+generate enc = do
+	let filename = show enc ++ ".regression"
+	    randomGood = randomGoodString (encodeable enc)
+	shortMixedEnc <- replicateM  300 (randomString   10)
+	shortGoodEnc  <- replicateM   30 (randomGood     10)
+	longMixedEnc  <- replicateM  300 (randomString 1000)
+	longGoodEnc   <- replicateM 3000 (randomGood   1000)
+	shortDec      <- replicateM  300 (randomString   10)
+	longDec       <- replicateM 3000 (randomString 1000)
+	writeFile filename (show
+		[ (s, encodeStrictByteStringExplicit enc s)
+		| ss <- [shortMixedEnc, shortGoodEnc, longMixedEnc, longGoodEnc]
+		, s <- ss
+		] ++ "\n")
+	appendFile filename (show
+		[ (bs, decodeStrictByteStringExplicit enc (pack bs))
+		| bss <- [shortDec, longDec]
+		, bs <- bss
+		] ++ "\n")