\input regression-test.tex
\documentclass{article}
\begin{document}
\START
\directlua{
  local tagpax = require("tagpax")
  local function report(message) texio.write_nl("log", message) end
  report("tagged=" .. tostring(tagpax.is_tagged("subdocument.pdf")))
  report("untagged=" .. tostring(tagpax.is_tagged("untagged-subdocument.pdf")))
  local ok, err = pcall(tagpax.is_tagged, "does-not-exist.pdf")
  report("missing-is-error=" .. tostring(not ok))
  report("missing-message=" .. tostring(err ~= nil and err:find("cannot open PDF", 1, true) ~= nil))
}
\END
\end{document}