90% of people will comply. Let's say it's only 50% though. Those people are no more or less likely to be infected. So it's 100% perfectly fine not to test everyone if the goal is to determine the number infected overall.

If looking to go beyond, hey let's get testing capacity to the point where those who are sick and desperately want to be tested can be tested, then we can attack the 1984 fantasy.

"But but what if I can't force those to be tested who don't want it" is an absurd and insane concern given that only a tiny minority of people can be tested who desperately want to.

Once we have testing capacity then those who want to force testing should go out and try to force people to be tested and happily accept whatever happens to them.