trying to patch tests for Diff package (transitive dependency)

haskellPackages.nix

self: super: {
  haskell = super.haskell // {
    packages = super.haskell.packages // {
      ghc844 = with self.haskell.lib; super.haskell.packages.ghc844.extend (hself: hsuper: {
        Diff = appendPatch hsuper.Diff /path/to/.config/nixpkgs/overlays/Diff-Test.patch;                                                                                           
      });
    };
  };
}

# Diff-Test.patch
diff --git a/test/Test.hs b/test/Test.hs                                                                  
index 4a4b3c0..f663e99 100644                                                                             
--- a/test/Test.hs                                                                                        
+++ b/test/Test.hs                                                                                        
@@ -134,7 +134,7 @@ prop_ppDiffR :: DiffInput -> Property
 prop_ppDiffR (DiffInput le ri) =                                                                         
     let haskDiff=ppDiff $ getGroupedDiff le ri                                                           
         utilDiff= unsafePerformIO (runDiff (unlines le) (unlines ri))                                    
-    in  cover (haskDiff == utilDiff) 90 "exact match" $                                                  
+    in  cover 90 (haskDiff == utilDiff) "exact match" $                                                  
                 classify (haskDiff == utilDiff) "exact match"                                            
                         (div ((length haskDiff)*100) (length utilDiff) < 110) -- less than 10% bigger    
     where