Dear café, I want to implement a roundtrip test for a parser/prettyprinter combination. Let me try to explain what I am struggling with. I start with some type definitions of functions I have *data Guarded a =* * Errors (NE.NonEmpty CtxError) | Checked a [Warning]* *parseFoo :: Text -> Guarded Foo* *prettyFoo :: Foo -> Text* The idea is that for all foo :: Foo, the following holds: *parseFoo . prettyFoo $ foo* should be equal to *Checked foo []* Now, if there is a counterexample, I would like to see prettyFoo foo as output, folowed by the show of the Errors part. I have been struggling to get this working, but without luck so far. I am not very familiar with Quickcheck, so that could be the problem too. Any help would be appreciated! Thanks Han