If there is evidence of resistance (for those that have had it), you wouldn't need to test everyone every day. Everyone that's been infected, and is dormant, goes back to work straight away. Those that test negative who've never had it also go back, because they won't get from co-workers, and even if they do, won't pass it along, so long as there's a critical mass of "had it"s to provide the narrow herd immunity.