Revert "Simplify test suite"

This reverts commit 8f2625dc87.

source/test-suite/Main.hs

@@ -1,12 +1,14 @@
+import qualified Control.Exception as Exception
 import qualified Control.Monad as Monad
 import qualified Data.List as List
 import qualified Language.Haskell.Brittany.Main as Brittany
 import qualified System.Directory as Directory
 import qualified System.FilePath as FilePath
+import qualified System.IO as IO
 import qualified Test.Hspec as Hspec
 
 main :: IO ()
-main = Hspec.hspec . Hspec.parallel $ do
+main = Hspec.hspec $ do
   let directory = "data"
   entries <- Hspec.runIO $ Directory.listDirectory directory
   Monad.forM_ (List.sort entries) $ \entry ->
@@ -15,20 +17,31 @@ main = Hspec.hspec . Hspec.parallel $ do
       Just slug -> Hspec.it slug $ do
         let input = FilePath.combine directory entry
         expected <- readFile input
-        let output = FilePath.combine "output" entry
-        Directory.copyFile input output
-        Brittany.mainWith
-          "brittany"
-          [ "--config-file"
-          , FilePath.combine directory "brittany.yaml"
-          , "--no-user-config"
-          , "--write-mode"
-          , "inplace"
-          , output
-          ]
-        actual <- readFile output
+        actual <- withTemporaryFile $ \output handle -> do
+          IO.hClose handle
+          Directory.copyFile input output
+          Brittany.mainWith
+            "brittany"
+            [ "--config-file"
+            , FilePath.combine directory "brittany.yaml"
+            , "--no-user-config"
+            , "--write-mode"
+            , "inplace"
+            , output
+            ]
+          readFile output
         Literal actual `Hspec.shouldBe` Literal expected
 
+withTemporaryFile :: (FilePath -> IO.Handle -> IO a) -> IO a
+withTemporaryFile callback = do
+  directory <- Directory.getTemporaryDirectory
+  let
+    acquire = IO.openTempFile directory "brittany-.hs"
+    release filePath handle = do
+      IO.hClose handle
+      Directory.removeFile filePath
+  Exception.bracket acquire (uncurry release) (uncurry callback)
+
 newtype Literal
   = Literal String
   deriving Eq