Pre-process ppx on testing only

Hi everyone !

I was wondering if with it was possible to preprocess a file only when
dune runtest is called.
I have a ppx that inline tests inside .ml files, but I dont especially wan’t to
keep that generated code as it is inlined inside src/ files and not in test/ files.

As for now, I declared my ppx with a inline_tests.backend in order to run tests only
on dune runtest. But I was wondering about the doability of that problem.

From my understanding dune runtest runs dune build, that would mean separate builds ?
That’s may be to much work on the developer-side.

Thank you for your time !