Make the test suite return an reasonable exit code

Test.QuickCheck.Batch.runTests doesn't return any error statistics,
which makes the test suite just display errorrs and always exit with
exit code 0. This is not good, since one cannot then actually batch run
tests.

This patch adds a wrapper over Batch.run which also modifies a passed
IORef Int to keep track of how many test failures or test aborts we had.
This makes it easy then to exit with an appropriate exit code.

test.hs

@@ -25,18 +25,49 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 
 module Main(main) where
 
+import Control.Monad
+import Data.IORef
 import Test.QuickCheck.Batch
+import System.IO
+import System.Exit
+
 import Ganeti.HTools.QC
 
+options :: TestOptions
 options = TestOptions
       { no_of_tests         = 500
       , length_of_tests     = 5
       , debug_tests         = False }
 
+
+incIORef :: IORef Int -> IO ()
+incIORef ir = atomicModifyIORef ir (\x -> (x + 1, ()))
+
+-- | Wrapper over a test runner with error counting
+wrapTest :: IORef Int
+         -> (TestOptions -> IO TestResult)
+         -> TestOptions -> IO TestResult
+wrapTest ir t to = do
+    tr <- t to
+    case tr of
+      TestFailed _ _ -> incIORef ir
+      TestAborted _ -> incIORef ir
+      _ -> return ()
+    return tr
+
+main :: IO ()
 main = do
-  runTests "PeerMap" options test_PeerMap
-  runTests "Container" options test_Container
-  runTests "Instance" options test_Instance
-  runTests "Node" options test_Node
-  runTests "Text" options test_Text
-  runTests "Cluster" options test_Cluster
+  errs <- newIORef 0
+  let wrap lst = map (wrapTest errs) lst
+  runTests "PeerMap" options $ wrap test_PeerMap
+  runTests "Container" options $ wrap test_Container
+  runTests "Instance" options $ wrap test_Instance
+  runTests "Node" options $ wrap test_Node
+  runTests "Text" options $ wrap test_Text
+  runTests "Cluster" options $ wrap test_Cluster
+  terr <- readIORef errs
+  (if (terr > 0)
+   then do
+     hPutStrLn stderr $ "A total of " ++ show terr ++ " tests failed."
+     exitWith $ ExitFailure 1
+   else putStrLn "All tests succeeded.")