Amend output of golden-tests to avoid confusion

brittany.cabal

@@ -170,6 +170,8 @@ test-suite brittany-test-suite
 
   build-depends:
     , hspec >= 2.8.3 && < 2.10
+    , HUnit >= 1.6.2 && < 1.7
+    , ansi-terminal >= 0.11.4 && < 0.12
     , parsec ^>= 3.1.14
     , these ^>= 1.1
   hs-source-dirs: source/test-suite

source/test-suite/Main.hs

@@ -15,6 +15,7 @@ import Language.Haskell.Brittany.Internal
 import Language.Haskell.Brittany.Internal.Config.Config
 import Language.Haskell.Brittany.Internal.Config.Types
 import Language.Haskell.Brittany.Internal.Prelude
+import Test.HUnit (assertEqual)
 import qualified System.Directory
 import System.FilePath ((</>))
 import System.Timeout (timeout)
@@ -22,6 +23,7 @@ import Test.Hspec
 import qualified Text.Parsec as Parsec
 import Text.Parsec.Text (Parser)
 import qualified Data.List.Extra
+import qualified System.Console.ANSI as ANSI
 
 hush :: Either a b -> Maybe b
 hush = either (const Nothing) Just
@@ -282,9 +284,15 @@ roundTripEqual c t =
     `shouldReturn` Right (PPTextWrapper t)
 
 goldenTest :: Config -> Text -> Text -> Expectation
-goldenTest c input expected =
-  fmap (fmap PPTextWrapper) (parsePrintModuleTests c "TestFakeFileName.hs" input)
-    `shouldReturn` Right (PPTextWrapper expected)
+goldenTest c input expected = do
+  result <- parsePrintModuleTests c "TestFakeFileName.hs" input
+  assertEqual
+    (  ANSI.setSGRCode [ANSI.SetColor ANSI.Foreground ANSI.Dull ANSI.Red]
+    ++ "golden input: see test source!"
+    ++ ANSI.setSGRCode [ANSI.Reset]
+    )
+    (Right (PPTextWrapper expected))
+    (fmap PPTextWrapper result)
 
 newtype PPTextWrapper = PPTextWrapper Text
   deriving Eq