Add test for fourmolu

Author: georgefst

test/functional/Format.hs

@@ -30,6 +30,7 @@ tests = testGroup "format document" [
     , stylishHaskellTests
     , brittanyTests
     , ormoluTests
+    , fourmoluTests
     ]
 
 rangeTests :: TestTree
@@ -127,6 +128,17 @@ ormoluTests = testGroup "ormolu" [
       GHC86 -> "formatted"
       _ -> "unchanged"
 
+fourmoluTests :: TestTree
+fourmoluTests = testGroup "fourmolu" [
+    goldenVsStringDiff "formats correctly" goldenGitDiff ("test/testdata/Format.fourmolu.hs") $ runSession hieCommand fullCaps "test/testdata" $ do
+        let formatLspConfig provider =
+                object [ "languageServerHaskell" .= object ["formattingProvider" .= (provider :: Value)] ]
+        sendNotification WorkspaceDidChangeConfiguration (DidChangeConfigurationParams (formatLspConfig "fourmolu"))
+        doc <- openDoc "Format.hs" "haskell"
+        formatDoc doc (FormattingOptions 4 True)
+        BS.fromStrict . T.encodeUtf8 <$> documentContents doc
+    ]
+
 
 formatLspConfig :: Value -> Value
 formatLspConfig provider = object [ "languageServerHaskell" .= object ["formattingProvider" .= (provider :: Value)] ]

test/testdata/Format.fourmolu.hs

@@ -0,0 +1,12 @@
+module Format where
+
+foo :: Int -> Int
+foo 3 = 2
+foo x = x
+bar :: String -> IO String
+bar s = do
+    x <- return "hello"
+    return "asdf"
+
+data Baz = Baz {a :: Int, b :: String}
+