Default project template for `cabal init`

Lib.hs

-- File: src/Lib.hs

module Lib (greeting) where

greeting :: String
greeting = "Hello, world!"

LibSpec.hs

-- File: test/src/LibSpec.hs

{-# LANGUAGE QuasiQuotes #-}
{-# LANGUAGE OverloadedStrings #-}
module Main (main) where

import qualified Lib
import Test.Hspec

main :: IO ()
main = hspec spec

spec :: Spec
spec = do
  describe "greeting test" $ do
    it "is hello world" $ do
       Lib.greeting `shouldBe` "Hello, world!"

Main.hs

-- File: app/Main.hs

module Main where

import qualified Lib

main :: IO ()
main = putStrLn Lib.greeting

myproject.cabal

cabal-version: 2.4
name: myproject
version: 0.1.0.0
synopsis: myproject synopsis.
description: myproject description.
license: BSD-3-Clause
license-file: LICENSE
author: Matt Renaud
maintainer: matt@m-renaud.com
build-type: Simple
extra-source-files: CHANGELOG.md

library internal-lib
  default-language: Haskell2010
  hs-source-dirs: src
  exposed-modules:
    Lib,
  build-depends:
    base >=4.12 && <4.13,
    
executable myproject
  default-language: Haskell2010
  hs-source-dirs: app
  main-is: Main.hs
  build-depends:
    base >=4.12 && < 4.13,
    internal-lib,
    
test-suite internal-lib-test
  default-language: Haskell2010
  hs-source-dirs: test/src
  type: exitcode-stdio-1.0
  main-is: LibSpec.hs
  build-depends:
    base >=4.12 && <4.13,
    internal-lib,
    hspec,
  ghc-options:
    -threaded -rtsopts -with-rtsopts=-N