"Could not find module ‘Test.HUnit’" Error when executing Haskell's unittest (HUnit) in CodeRunner

I have simple unit test code for Haskell's HUnit. I use Mac OS X 10.10, and I installed HUnit with cabal install hunit.

module TestSafePrelude where

import SafePrelude( safeHead )
import Test.HUnit

testSafeHeadForEmptyList :: Test
testSafeHeadForEmptyList = 
    TestCase $ assertEqual "Should return Nothing for empty list"
                           Nothing (safeHead ([]::[Int]))

testSafeHeadForNonEmptyList :: Test
testSafeHeadForNonEmptyList =
    TestCase $ assertEqual "Should return (Just head) for non empty list" (Just 1)
               (safeHead ([1]::[Int]))

main :: IO Counts
main = runTestTT $ TestList [testSafeHeadForEmptyList, testSafeHeadForNonEmptyList]

I can execute it with runhaskell TestSafePrelude.hs to get the results:

Cases: 2  Tried: 2  Errors: 0  Failures: 0
Counts {cases = 2, tried = 2, errors = 0, failures = 0}

However, when I run it in Code Runner, I have error message that can't find the HUnit module.

CodeRunner launches the test on a different shell environment, and this seems to be the issue. If so, what environment variables need to be added? If not, what might be causing the problem?

I also find that ghc-pkg list from the CodeRunner does not search for the directories in ~/.ghc which contains the HUnit.

/usr/local/Cellar/ghc/7.8.3/lib/ghc-7.8.3/package.conf.d:
    Cabal-1.18.1.4
    array-0.5.0.0
    ...
    xhtml-3000.2.1

This is the results when executed in shell:

/usr/local/Cellar/ghc/7.8.3/lib/ghc-7.8.3/package.conf.d
   Cabal-1.18.1.4
   array-0.5.0.0
   ...
/Users/smcho/.ghc/x86_64-darwin-7.8.3/package.conf.d
   ...
   HUnit-1.2.5.2
   ...
   zlib-0.5.4.2

I added both ~/.cabal and ~/.ghc in the path, but it doesn't work.

The problem was the $HOME setup change. I used different $HOME for CodeRunner, but Haskell searches for $HOME/.cabal and $HOME/.ghc for installed package.

After my resetting $HOME to correct location, everything works fine.