haskell - How to use ByteStrings with QuickTest in DocTest? -

how define arbitrary instance (as stated here) when using doctest , quickcheck?

doctest , cabal set described here separate directory tests.

the doctest line looks this:

-- prop> (\s -> (decode . encode $ s == s)) :: bytestring -> bool decode :: bytestring -> bytestring encode :: bytestring -> bytestring 

where , how define arbitrary instance, doctest can find it? note want define in test project.

try

-- $setup -- >>> import control.applicative -- >>> import qualified data.bytestring bytestring -- >>> import test.quickcheck -- >>> instance arbitrary bytestring arbitrary = bytestring.pack <$> arbitrary -- >>> instance coarbitrary bytestring coarbitrary = coarbitrary . bytestring.unpack  -- | -- prop> \ s -> (decode . encode) s == s decode:: bytestring -> bytestring encode :: bytestring -> bytestring 

named chunks can used such definitions. however, each complete definition must on 1 line, , doctest report each use of >>> success or failure - in case, 6 attempts reported, though 1 of them test.