1 files changed, 44 insertions, 0 deletions
diff --git a/tests/Language/Haskell/Stylish/Tests/Util.hs b/tests/Language/Haskell/Stylish/Tests/Util.hs
index 40b5629..f43b6b5 100644
--- a/tests/Language/Haskell/Stylish/Tests/Util.hs
+++ b/tests/Language/Haskell/Stylish/Tests/Util.hs
@@ -1,9 +1,22 @@
 module Language.Haskell.Stylish.Tests.Util
     ( testStep
+    , withTestDirTree
     ) where
 
 
 --------------------------------------------------------------------------------
+import           Control.Exception              (bracket, try)
+import           System.Directory               (createDirectory,
+                                                 getCurrentDirectory,
+                                                 getTemporaryDirectory,
+                                                 removeDirectoryRecursive,
+                                                 setCurrentDirectory)
+import           System.FilePath                ((</>))
+import           System.IO.Error                (isAlreadyExistsError)
+import           System.Random                  (randomIO)
+
+
+--------------------------------------------------------------------------------
 import           Language.Haskell.Stylish.Parse
 import           Language.Haskell.Stylish.Step
 
@@ -15,3 +28,34 @@ testStep step str = case parseModule [] Nothing str of
     Right module' -> unlines $ stepFilter step ls module'
   where
     ls = lines str
+
+
+--------------------------------------------------------------------------------
+-- | Create a temporary directory with a randomised name built from the template
+-- provided
+createTempDirectory :: String -> IO FilePath
+createTempDirectory template  = do
+  tmpRootDir <- getTemporaryDirectory
+  dirId <- randomIO :: IO Word
+  findTempName tmpRootDir dirId
+  where
+    findTempName :: FilePath -> Word -> IO FilePath
+    findTempName tmpRootDir x = do
+      let dirpath = tmpRootDir </> template ++ show x
+      r <- try $ createDirectory dirpath
+      case r of
+        Right _ -> return dirpath
+        Left  e | isAlreadyExistsError e -> findTempName tmpRootDir (x+1)
+                | otherwise              -> ioError e
+
+
+--------------------------------------------------------------------------------
+-- | Perform an action inside a temporary directory tree and purge the tree
+-- afterwards
+withTestDirTree :: IO a -> IO a
+withTestDirTree action = bracket
+    ((,) <$> getCurrentDirectory <*> createTempDirectory "stylish_haskell")
+    (\(current, temp) ->
+        setCurrentDirectory current *>
+        removeDirectoryRecursive temp)
+    (\(_, temp) -> setCurrentDirectory temp *> action)