This might be a really silly question I have 2 friends who would like their DNA done, they don't and will not join Ancestry or similar, will it still work if they do a test and not belong to a genealogy site.
LM
Why do they want their DNA tested?
If it is to understand their Ethnicity then the results could be very unexpected but should still be viewed with scepticism. Basically, a rough guide.
Their DNA can be set to Private so only they can see it.
If they have no intention of undertaking Genealogical research then taking a DNA test is pretty pointless.
There is a big but though, in that, if they have doubts about their parentage then a single DNA test is not likely to resolve the matter.