The problem is that taking the test before air travel or right after the arrival at the destination is like playing the Russian roulette. For example in my country you can take a COVID tests but:

1. you might need to wait for results for 4-5 days, while most destinations require taking it at most 72 hours before the arrival

2. if you turn out to be asymptomatic, but test positive, then you instantly get into at least 10 day quarantine (you cannot take tests anonymously). You have no time to cancel your travel plans.

Also, if you choose not do do it, but instead take test at your destination, you might get stuck in quarantine in the foreign country

So I would never travel to a country that requires tests. Only those which require just written statement, or location form, and maybe temperature check.