That's an excellent question.
Edited to add: I left the reply page open and went off to drive the cowboy truck and stock trailer. I came home, filled in my reply, but Lillian had already beat me to the punch. She is absolutely correct, as you'll see from my much wordier reply.First of all, "none" is a shortened version of "not one." Therefore,
one (and therefore
none) is singular, or so it's been said since the beginning of time.
However, the rule is to look at what there is "none of" in your sentence.
Is it singular or plural?
None of the cake is missing. (Cake is singular, therefore use
is.)
None of the houses are painted. (Houses is plural, therefore use
are.)
The same rule would hold true for other verbs:
was/were, has/have, etc.
Apparently, the SAT testing service considers none as a singular word only. However, according to Merriam Webster’s Dictionary of English Usage, “Clearly none has been both singular and plural since Old English and still is. The notion that it is singular only is a myth of unknown origin that appears to have arisen in the 19th century. If in context it seems like a singular to you, use a singular verb; if it seems like a plural, use a plural verb. Both are acceptable beyond serious criticism” (p. 664)
Help at all?