How to test small program with user input in Haskell

Im taking a software testing class. And we were allowed to choose what language to write our code and tests in. And I choose Haskell. I know, maybe not the best way to learn testing (= but...

The unit-testing and coding has been working great!

But I am also required to use mocking to get a higher grade.

My problem is that I dont know very much Haskell (like Monads and stuff).

I have written and tested Calculator. And now I want to test my main. My instructor used Mockito for Java to check that the program had the correct flow.

Is it possible to test that my if-statements are correct? I have tried reading up on testing IO actions through Monads, but I dont quite understand it. Maybe I should just learn more about Monads before trying to solve this?

Any help or reading suggestions are very much appreciated!

import Calculator

main :: IO ()
main = do
        putStrLn("What should I calcuclate? ex 3*(2+2)  | quit to exit" )
        line <- getLine
        if line /= "quit"
        then do if correctInput line
                then do putStrLn( show $ calculate line) 
                        main
                else do putStrLn( "Wrong input") 
                        main
        else putStrLn("goodbye")