Use GHC 8.3, not GHC 7. Not sure why 7 is enabled, let me try and disable it.
I got this error when running the tests.
Not in scope: `main'
Perhaps you meant `min' (imported from Prelude)
I modified it, by adding
main :: IO ()
main = hspec spec
And then the basic test runs normally.
But when I want to attampt to the final tests. The same error occurs.