The rules for refunds have not changed in the past year.
1. If you purchase refundable tickets, they are refundable under their fare rules.
2. If you purchase non-refundable and AA cancels or significantly (4+ hours) changes the schedule, you are entitled to a full refund nonetheless.
If, for whatever reason, you do not want to undergo a simple Covid test, I would not even think about booking now. Nobody can say for certain, but it is highly unlikely that the US will drop its entry test requirement anytime in 2021, with 2022 a huge maybe. You may want to look at travel within the US and skipping domestic destinations which have pre-departure or quarantine test-out requirements.If it by some remote chance comes to pass that the scientists advising the CDC recommend relaxing the testing requirements for entry to the US, you could consider booking at that time.