Add casesplit CodeAction test

Author: Avi-D-coder

test/functional/HaReSpec.hs

@@ -49,6 +49,13 @@ spec = describe "HaRe" $
           expected = "\nmain = putStrLn \"hello\"\n\n\
                      \foo x = y + 3\n  where\n    y = 7\n"
         in execCodeAction "HaReDemote.hs" r "Demote y one level" expected
+    context "casesplit argument" $ it "works" $
+      let r = Range (Position 4 5) (Position 4 6)
+          expected = "\nmain = putStrLn \"hello\"\n\n\
+                     \foo :: Maybe Int -> ()\n\
+                     \foo Nothing = ()\n\
+                     \foo (Just x) = ()\n"
+        in execCodeAction "GhcModCaseSplit.hs" r "Case split on x" expected
 
 
 getCANamed :: T.Text -> [CAResult] -> CodeAction