[SOLVED] Testing user input with Hspec

Testing user input with Hspec

I have a program that takes a user input from getLine then validates that it is all numbers. If it passes it runs a function of String -> String and prints the result to screen. If not it repeats the getLine.

module Main where

import Control.Monad.Loops (untilJust)
import Data.Char           (isDigit)

main = do
  let validateInput s = if all isDigit s then Just s else Nothing
  putStrLn =<< myFunc <$> untilJust (validateInput <$> (putStr "Number : " >> getLine))

myFunc = id -- to do

How do I test the this main function with something like Hspec to check that it does the right thing with a number input vs other inputs (letters, empty etc)

test1 rejects a non-numeric input of "abc"
test2 returns 123 as 123

Solution

Since you want to test the logic rather than the user interaction, I'd suggest that you simply factor out the input validation.