Travel has always required flexibility, but never more than now. When we started our trip the US had the 3 day test rule in effect. As I was casually watching the BBC one day Biden was having a press conference and the onscreen graphic said the rule was now ONE day before. Well that certainly changed everything! I had a list from the French government of labs in my arrondisment that were testing, but we asked at the front desk and they said Oh yeah, there's a pharmacy just down the street that will do your test for you. Which is good, because I had done some legwork and although Paris is crawling with pharmacies, most of them don't test or vaccinate (or they only do one or the other, or don't deal with tourists).
We went right away and things were quiet and they said sure, come back tomorrow we'll do the test no problem. Well something had happened in the time between our two visits, because the next day the place was full of locals not only getting tested but getting the jab. We had to wait about an hour for the swab up the nose and the official form with the results. The good news is, this pharmacy was very busy and hopefully making some profit. The bad news is, it was a small space which was now jammed with people needing their services. As I was getting swabbed I mentioned how busy they were and the poor pharmacist rolled her eyes and said, TOO busy. She and her elderly cohort were overwhelmed but kept their cool, as did the clientele.
The test form looks very similar to the pass sanitaire, so don't get them confused.