Changes tests to add whitespaces in generated JSON string

test/Spec.hs

@@ -1,7 +1,8 @@
 module Main where
 
-import Control.Monad (unless)
+import Control.Monad (unless, forM)
 import Data.Char (isControl)
+import Data.List (intercalate)
 import System.Exit
 import Test.QuickCheck
 import Test.QuickCheck.Test (isSuccess)
@@ -10,33 +11,56 @@ import JSONParser
 
 main :: IO ()
 main = do
-  result <- quickCheckResult $ \j -> parseJSON (show j) == Just j
+  result <- quickCheckResult checkJSON
   unless (isSuccess result) exitFailure
 
+checkJSON :: JValue -> Gen Property
+checkJSON value = do
+  json <- stringify value
+  return . counterexample (show json) . (== Just value) . parseJSON $ json
+
+stringify :: JValue -> Gen String
+stringify = pad . go
+  where
+    surround l r j = l ++ j ++ r
+    pad gen = surround <$> jsonWhitespaceGen <*> jsonWhitespaceGen <*> gen
+    commaSeparated = pad . pure . intercalate ","
+
+    go value = case value of
+      JArray elements ->
+        mapM (pad . stringify) elements >>= fmap (surround "[" "]") . commaSeparated
+      JObject kvs ->
+        mapM stringifyKV kvs >>= fmap (surround "{" "}") . commaSeparated
+      _           -> return $ show value
+
+    stringifyKV (k, v) = surround <$> pad (pure $ show k) <*> stringify v <*> pure ":"
+
 instance Arbitrary JValue where
   shrink = genericShrink
 
   arbitrary = sized go
     where
-      go 0 = oneof scalarGens
-      go n = frequency [(2, oneof scalarGens), (3, oneof (compositeGens n))]
+      go n | n < 5 = frequency [(4, oneof scalarGens), (1, oneof (compositeGens n))]
+      go n = frequency [(1, oneof scalarGens), (4, oneof (compositeGens n))]
 
       scalarGens = [ pure JNull
                    , JBool   <$> arbitrary
-                   , JString <$> arbitraryJSONString
-                   , JNumber <$> arbitrary <*> oneof [choose (-5, 0), arbitrary]
+                   , JString <$> jsonStringGen
+                   , JNumber <$> arbitrary <*> listOf digits <*> arbitrary
                    ]
 
       compositeGens n = [ fmap JArray  . scaledListOf . go    $ n `div` 2
                         , fmap JObject . scaledListOf . objKV $ n `div` 2
                         ]
 
-      objKV n = (,) <$> arbitraryJSONString <*> go n
+      objKV n = (,) <$> jsonStringGen <*> go n
+
+      scaledListOf = scale (`div` 2) . listOf
 
-      scaledListOf = scale (\n -> n * 2 `div` 3) . listOf
+      digits = choose (0, 9)
 
-arbitraryJSONString :: Gen String
-arbitraryJSONString = listOf arbitraryJSONChar
+jsonStringGen :: Gen String
+jsonStringGen = listOf arbitraryJSONChar
   where
     arbitraryJSONChar' =
       frequency [(9, arbitraryASCIIChar), (0, choose ('\128', '\65535'))]
@@ -46,3 +70,10 @@ arbitraryJSONString = listOf arbitraryJSONChar
         (99, arbitraryJSONChar')
       , (1, elements ['"' , '\\' , '\b' , '\f' , '\n' , '\r' , '\t'])
       ]
+
+jsonWhitespaceGen :: Gen String
+jsonWhitespaceGen =
+  scale (round . sqrt . fromIntegral)
+  . listOf
+  . elements
+  $ [' ' , '\n' , '\r' , '\t']