`Arbitrary` instances for GADTs

I have a need to define QuickCheck Arbitrary instances for GADTs, of course genericArbitrary does not work, because GHC does not derive Generic for GADTs. But kind-generics: Generic programming in GHC style for arbitrary kinds and GADTs. uses Template Haskell to define a instances for a class GenericK , so I think the missing piece would be a function genericKArbitrary, analogous to generic-randoms genericArbitrary. Does that exist somewhere? What else do people use to write property tests ove...