So I was about to book this cruise but when I saw the above post we have probably decided against it. It does say "it can be a test you administer to yourself at home without supervision." How will they even know you took it within the 2 days?
https://www.royalcaribbean.com/faq/questions/will-i-have-to-take-a-test-before-i-cruise#transatlantic
For Transatlantic and Transpacific Cruises
All guests age 2 and older must bring a negative test result for a COVID-19 test taken no more than 2 days prior to sailing.
Required testing can be completed using any type of PCR or antigen COVID-19 test. It can be professionally proctored at your doctor or drugstore, or it can be a test you administer to yourself at home without supervision.
Guests under age 2 do not have any testing requirements.