[Haskell-cafe] Deriving Eq and Show instances for testing

I have datatypes for which I need an Eq and Show instance only for testing. I could derive those instances in the datatype declaration but I prefer not to add unnecessary functionality. With StandaloneDeriving extension I can derive the instances in the test module but this produces many warning about orphan instances. Is there a better approach or a way to stop reports about orphan instance warnings? Regards