While Switzerland has strict closure rules, (major) rail stations and airports are in a different “universe”
, shops in these venues are open 365 days/year and some as late as 11 pm. In the NYC area where I live few stores are open on Christmas Day, especially tourist attractions; for transportation purposes Christmas in SW counts as any other Federal holiday. I was in ZRH on Christmas a few years ago, boats on Lake Zurich were running on a (Federal) holiday schedule = MORE service than on (normal) weekdays. Several museums are open 365 days a year and/or Christmas Day.
While touristic/tourism establisments may be the case, in context of where can you get tested, unfortunately that won‘t be the case. Airports really just ZRH and GVA these days in CH which are „meaningful“ and while shops within ZRH/GVA airport premise have permission to open beyond 8pm (also do have permission to open on Sunday and public holidays), not all will open too much longer beyond 8pm. Furthermore, train stations also depending on which one as mentioned, Hauptbahnhof (HB) in major cities may open late (basically same permission conditions as airport), namely those again in Zurich, Geneva, but do not expect all will be opened or open late.