Install first

• Haskell Platform. It includes (among other things) Cabal - Haskell build system.
• HSpec - Haskell testing library

cabal update && cabal install hspec

• Ruby - install through rvm, your OS package manager or use system-provided Ruby interpreter.
• RubyGems
• Guard and guard-haskell - for watching your code and executing tests on change

gem install guard-haskell

Play with it

guard

Hello
  helloer
    - says hello

Finished in 0.0003 seconds
1 example, 0 failures

cabal test

Building hspec-kickstart-0.1.0...
Preprocessing library hspec-kickstart-0.1.0...
In-place registering hspec-kickstart-0.1.0...
Preprocessing test suite 'spec' for hspec-kickstart-0.1.0...
[1 of 3] Compiling Hello            ( src/Hello.hs, dist/build/spec/spec-tmp/Hello.o )
[2 of 3] Compiling HelloSpec        ( test/HelloSpec.hs, dist/build/spec/spec-tmp/HelloSpec.o )
[3 of 3] Compiling Main             ( test/Spec.hs, dist/build/spec/spec-tmp/Main.o )
Linking dist/build/spec/spec ...
Running 1 test suites...
Test suite spec: RUNNING...
Test suite spec: PASS
Test suite logged to: dist/test/hspec-kickstart-0.1.0-spec.log
1 of 1 test suites (1 of 1 test cases) passed.