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-rw-r--r--users/grfn/xanthous/test/Test/Prelude.hs29
1 files changed, 21 insertions, 8 deletions
diff --git a/users/grfn/xanthous/test/Test/Prelude.hs b/users/grfn/xanthous/test/Test/Prelude.hs
index c423796184f7..2df0a6290a02 100644
--- a/users/grfn/xanthous/test/Test/Prelude.hs
+++ b/users/grfn/xanthous/test/Test/Prelude.hs
@@ -1,3 +1,5 @@
+{-# LANGUAGE AllowAmbiguousTypes #-}
+--------------------------------------------------------------------------------
 module Test.Prelude
   ( module Xanthous.Prelude
   , module Test.Tasty
@@ -5,15 +7,26 @@ module Test.Prelude
   , module Test.Tasty.QuickCheck
   , module Test.QuickCheck.Classes
   , testBatch
+  , jsonRoundTrip
   ) where
-
-import Xanthous.Prelude hiding (assert, elements)
-import Test.Tasty
-import Test.Tasty.QuickCheck
-import Test.Tasty.HUnit
-import Test.QuickCheck.Classes
-import Test.QuickCheck.Checkers (TestBatch)
-import Test.QuickCheck.Instances.ByteString ()
+--------------------------------------------------------------------------------
+import           Xanthous.Prelude hiding (assert, elements)
+--------------------------------------------------------------------------------
+import           Test.Tasty
+import           Test.Tasty.QuickCheck
+import           Test.Tasty.HUnit
+import           Test.QuickCheck.Classes
+import           Test.QuickCheck.Checkers (TestBatch, EqProp ((=-=)))
+import           Test.QuickCheck.Instances.ByteString ()
+--------------------------------------------------------------------------------
+import qualified Data.Aeson as JSON
+import           Data.Aeson (ToJSON, FromJSON)
+--------------------------------------------------------------------------------
 
 testBatch :: TestBatch -> TestTree
 testBatch (name, tests) = testGroup name $ uncurry testProperty <$> tests
+
+jsonRoundTrip
+  :: forall a. (ToJSON a, FromJSON a, EqProp a, Arbitrary a, Show a) => TestTree
+jsonRoundTrip = testProperty "JSON round trip" $ \(x :: a) ->
+  JSON.decode (JSON.encode x) =-= Just x