The testing regime at the moment at the border, certainly for the unvaccinated, consists of a pre-arrival test and then day-one and day-eight tests. For the vaccinated, that's been shifting over time. Right now, non-U.S. individuals, or even vaccinated individuals, are getting tested because we're living through an uncertain time with the omicron variant and all of these need to be reevaluated.
On January 18th, 2022. See this statement in context.