[HELP] Request for patches to improve Org test coverage

[Ihor Radchenko <yantar92@gmail.com>]

Dear Fellow Orgers,

Despite being not directly visible to users, Org mode testing suite is
critical to maintain overall codebase stability. It helps to avoid
unintentional breakages as we keep adding new features to Org.

Yet, writing tests is probably not the most exciting part for
volunteer contributors. Not many new patches also include tests and the
core Org maintainers do not have a bandwidth to supply every new
significant patch with tests.

I am writing this help request in a hope that someone interested and/or
experienced with writing tests can help improving Org tests without a
need to spend a lot of time doing something unfamiliar (e.g. I
personally wrote my very first test as a patch for Org, not knowing much
about code testing beforehand).

Some of the possible improvements to Org test suite are listed below:

- Tests on bugfix branch fail to run using Emacs 26.
  Not because of main Org code, but because test-org re-defines
  decode-time in a way not supported by older Emacs versions. (This has
  been fixed on main and simply need to be ported back to bugfix).

- Tests always run in a single process and cannot benefit from make -j
  Supporting parallel execution of multiple test sets would make Org
  development much faster by reducing make test runtime.

- Testing native-compiled Org is missing. Having it would be nice.

- Tests covering state logging are missing. I wrote an example patch how
  to write such tests, but never got around for more
  https://orgmode.org/list/87tul1v11c.fsf@localhost

- Most of the tests are written assuming default values of customised
  variables. We have very basic test coverage for non-standard settings.
  A way to run all possible tests under most common user customisations
  would improve the test coverage a lot.

- Generally, more and better tests would be welcome.

Best,
Ihor