Add unit tests for JSON serialization

[aashirvad08]

This PR adds unit tests covering the JSON serialization functionality.

The tests verify that expected fields are correctly serialized to JSON,
following the discussion in #517. The tests run entirely in memory and
check that struct members are properly converted to JSON.

Closes #517

[andresailer]

Please drop the two commits from the TransportFrameData PR

[tmadlener]

Thanks a lot. Seconding the comment from @andresailer to drop the TransportFrameData commit(s) from this PR to have it only contain JSON related things.

A few more comments / suggestions inline.

[aashirvad08]

Thanks for the detailed review,
I’ve addressed the comments:
moved the JSON test into tests/unittests and integrated it with the unittest_podio target
removed the SPDX header
replaced the magic number with podio::ObjectID::untracked
added the index == 0 check
replaced manual vector checks with Catch2 matchers
removed unnecessary Approx usage
Locally the tests build and run successfully (unittest_podio). Please let me know if any further adjustments are needed.

[tmadlener]

It loosk like you picked up a few files that are generated by cmake in your last commit. Please remove them again.

• tests/CMakeFiles as a whole
• tests/unittests/CMakeCache
• tests/CMakeLists.txt.save
• tests/tmp_peering_forward.pdf

[aashirvad08]

Thanks for pointing this out.
I’ve removed the accidentally committed CMake-generated files (tests/CMakeFiles). The other files mentioned were not tracked in the repository.
Please let me know if anything else needs adjustment.

[aashirvad08]

hey ,
Removed the accidentally committed CMakeCache.txt file.
The other mentioned files were not tracked in the repository.

[andresailer]

The other mentioned files were not tracked in the repository.

Why do you think there are comments on the files in this PR to remove them, if they were not tracked in the repository?

[aashirvad08]

I have removed the accidentally committed generated files.

[tmadlener]

Thanks a lot for cleaning up. There are a few more minor things that could be improved (and that became more easily visible now that the "noise" has been cut down).

[aashirvad08]

Thanks for the suggestions
I have updated tests/unittests/test_json_output.cpp accordingly.

[andresailer]

Please make sure you squash the commits to remove those accidentally committed files from the history.

[jmcarcell]

Fun fact: if you want to reduce compile times of podio or EDM4hep-related, the easiest and probably only practical thing you can do is to compile without json, everything else is the standard library and not much can be done.