> For XFA I noticed that almost none of the XFA methods are tested,
and also have no example PDFs, is this something I missed in the
codebase or is the XFA implementation tested somewhere else? Or is it
just not tested?
FWIW, there certainly do seem to be XFA tests in pdfium. If you have a full checkout, in testing/resources/, there will be xfa/, pixel/xfa_specific/, javascript/xfa_specific/ to name a few.
A GH search yields various test cases where these are accessed, including in fpdfsdk/fpdf_formfill_embeddertest.cpp, xfa/fwl/cfwl_edit_embeddertest.cpp, testing/fuzzers/*xfa*, and so on.