Hashem runs the entire world and decides the life and health condition of every person throughout their life, with some conditions being for tests of faith and trust etc… To others being punishments in this temporary world instead of in the next olam haemes…. And many other reasons….
When a person starts to live a life a bitachon and emunah in Hashem and always turns to Hashem directly for help instead of going through messengers-gedolim, doctors or segulahs etc…..-then it is not a lack of hishtadlus if he doesn’t take a Covid-19 test cause he knows so deep inside him that his entire life is run by Hashem and everything is decided by Hashem.
May we all start to turn directly to Hashem in our time of needs, be it for health, livlihood or children etc…