If you don't know the basic features of a language you don't know that language anymore. You maybe once knew it really well, and you still know the general syntax, but you aren't a insert language programmer anymore.

I do agree though that testing specific language skills is mostly pointless. The only time I've been given a programming test as part of an interview I was given a basic language spec that filled a couple pages then a book of problems to solve in the new language. Thats the way you should test programming skill in my opinion.