Run program with mocked stdin

runwithstdin.hs

import           Control.Exception
import           GHC.IO.Handle
import           System.IO
import           System.IO.Temp

main :: IO ()
main = do
  runWithStdin "Ornette Coleman Trio\nAt the Golden Circle Stockholm" $ do
    getLine >>= putStrLn
  getLine >>= putStrLn
  runWithStdin "Albert Ayler\nSpiritual Unity" $ do
    getLine >>= putStrLn
  getLine >>= putStrLn

runWithStdin :: String -> IO () -> IO ()
runWithStdin input action = do
  withSystemTempFile "runWithInput" $ \path handle -> do
    hPutStrLn handle input
    hClose handle
    handle' <- openFile path ReadMode
    stdin' <- hDuplicate stdin
    hDuplicateTo handle' stdin
    finally action $ do
      hDuplicateTo stdin' stdin
      hClose handle'