[!NOTE]
Unfortunately kotlinx.serialization also does not have conformance tests built-in. Considering it is an experimental API, we can support both our code and their code at the same time by contributing to the library. I have made an attempt to contribute by opening this PR: https://github.com/Kotlin/kotlinx.serialization/pull/2404. This is a good starting point, it is very easy to see what kotlinx.serialization library is lacking by running those kinds of tests.
Run the full set of conformance tests and report or document it somewhere.
Those tests will ensure we are almost 100% compatible with the protobuf wire format. Optionally protobuf json compatability can be tested as well.
More details on conformance tests here.