Add regression test for Fourmolu fixities

Author: georgefst

Diff for: plugins/hls-fourmolu-plugin/test/Main.hs

@@ -29,6 +29,8 @@ tests =
             formatDoc doc (FormattingOptions 4 True Nothing Nothing Nothing)
         , goldenWithFourmolu cli "formats imports correctly" "Fourmolu2" "formatted" $ \doc -> do
             formatDoc doc (FormattingOptions 4 True Nothing Nothing Nothing)
+        , goldenWithFourmolu cli "uses correct operator fixities" "Fourmolu3" "formatted" $ \doc -> do
+            formatDoc doc (FormattingOptions 4 True Nothing Nothing Nothing)
         ]
 
 goldenWithFourmolu :: Bool -> TestName -> FilePath -> FilePath -> (TextDocumentIdentifier -> Session ()) -> TestTree

Diff for: plugins/hls-fourmolu-plugin/test/testdata/Fourmolu3.formatted.hs

@@ -0,0 +1,7 @@
+b :: Bool
+b =
+    id $
+        id $
+            case True && True of
+                True -> True
+                False -> False

Diff for: plugins/hls-fourmolu-plugin/test/testdata/Fourmolu3.hs

@@ -0,0 +1,6 @@
+b :: Bool
+b =
+    id $ id $
+        case True && True of
+            True -> True
+            False -> False