[jupp0r]

It sounds like your use case is property based testing. Have you tried any of the QuickCheck ports to C++? My favorite is RapidCheck (https://github.com/emil-e/rapidcheck). You define generators for your struct fields and write a pure function to check whether the parsed output conforms to your expectations.

[linuxlizard]

Checking that out now! Reminds me a little of the Python library Hypothesis. https://hypothesis.readthedocs.io/en/latest/