Start with ghcup
curl --proto '=https' --tlsv1.2 -sSf https://get-ghcup.haskell.org | sh
This script will download and install the following binaries:
- ghcup - The Haskell toolchain installer
- ghc - The Glasgow Haskell Compiler
- cabal - The Cabal build tool for managing Haskell software
- stack - (optional) A cross-platform program for developing Haskell projects
- hls - (optional) A language server for developers to integrate with their editor/IDE
I chose not to install stack as I want cabal because I found this testing framework
Once Cabal is installed:
Create a Project directory
mkdir myProject && cd myProject
If you want the full Cabal experience follow the instructions here which have been sumarised here:
Optional This creates the folder structure and needed files
cabal init
Optional This will build the executable and run it
cabal run
Mandatory for Hspec The next bit is from the HSpec site
this creates a hidden package file in the current directory:
.ghc.environment.x86_64-darwin-9.0.1
Note the version number of ghc. If you update your version of ghc the following command will need running again
cabal update && cabal install --package-env=. --lib hspec hspec-contrib QuickCheck HUnit
Now create the test spec in Spec.hs for this example
main :: IO ()
main = hspec $ do
describe "" $ do
it "returns the first element of a list" $ do
head [23 ..] `shouldBe` (23 :: Int)
it "returns the first element of an *arbitrary* list" $
property $ \x xs -> head (x:xs) == (x :: Int)
it "throws an exception if used with an empty list" $ do
evaluate (head []) `shouldThrow` anyExceptio
To run the test:
run haskell Spec.hs
If you want your Specs to run every time you make changes in a true Test First Style you could use faswatch or similar.
Installing fswatch
used brew install fswatch
Run this from the project directory where your Haskell files are being edited Setup fswatch to watch changes to Haskell source files and run test specs (I made the following an alias)
fswatch -or *.hs | xargs -n1 -I{} runhaskell *Spec.hs