Minimized test case to demonstrate issue writing to locked file.

See takano-akio#2.

tests/test.hs

@@ -1,65 +1,21 @@
-{-# LANGUAGE ViewPatterns #-}
-
-import Control.Monad
 import Control.Concurrent
-import Control.Concurrent.Async
-import Debug.Trace (trace)
-import System.Environment
-import System.Exit
-import System.Process
 
 import System.FileLock
 
 main :: IO ()
-main = do
-  args <- getArgs
-  case args of
-    ["shared", read -> duration]
-      -> holdLock "shared" Shared duration
-    ["exclusive", read -> duration]
-      -> holdLock "exclusive" Exclusive duration
-    ["try"]
-      -> tryTakingLock
-    _ -> void $ mapConcurrently id
-      [ callSelf ["shared", "300"]
-      , callSelf ["shared", "200"]
-      , msleep 10 >> callSelf ["exclusive", "500"]
-      , msleep 20 >> callSelf ["try"]
-      , msleep 50 >> callSelf ["shared", "500"]
-      , msleep 700 >> callSelf ["shared", "10"]
-      , msleep 1500 >> callSelf ["try"]
-      ]
-
-callSelf :: [String] -> IO ()
-callSelf args = do
-  result <- trace "Attempting to call self" $ rawSystem ".\\bin\\test-filelock.exe" args
-  case result of
-    ExitSuccess -> putStrLn "callSelf succeeded"
-    x -> putStrLn $ "callSelf encountered unexpected exit code: " ++ show x
-  return ()
-
-msleep :: Int -> IO ()
-msleep = threadDelay . (*1000)
-
-holdLock :: String -> SharedExclusive -> Int -> IO ()
-holdLock ty sex duration = do
-  withFileLock lockfile sex $ \_ -> do
-    putStrLn $ "took " ++ desc
-    if sex == Exclusive then testWrite else return ()
-    msleep duration
-  putStrLn $ "released " ++ desc
-  where
-    desc = ty ++ " lock"
-    testWrite = trace "attempting write..." $ writeFile lockfile "testing"
-
-tryTakingLock :: IO ()
-tryTakingLock = do
-  ml <- tryLockFile lockfile Exclusive
-  case ml of
-    Nothing -> putStrLn "lock not available"
-    Just l -> do
-      putStrLn "lock was available"
-      unlockFile l
-
-lockfile :: String
-lockfile = "lock"
+main = lockAndWriteFile "testLockFile.txt" "testing, testing; 1, 2, 3"
+
+lockAndWriteFile :: String -> String -> IO ()
+lockAndWriteFile fname contents = do
+  withFileLock fname Exclusive $ \_ -> do
+    putStrLn "took exclusive lock; attempting write..."
+
+    -- Following line fails, printing "test-filelock.exe: testLockFile.txt:
+    -- hClose: permission denied (Permission denied)" and process exits
+    -- prematurely with exit code 1.
+    --
+    -- However, there are no issues when it's commented out.
+    writeFile fname contents
+
+  -- Never prints (unless writeFile line is commented out).
+  putStrLn "released exclusive lock"