When should I test? Don't want to overreact...?

I’ve been on the Nuvaring for close to a year now. Since I have been on it my period has never ONCE been late. It’s been like clockwork – down to the very hour. I always get it on the Wednesday morning after I take my ring out (I take it out Monday’s) It’s now Thursday afternoon and still nothing. How long should I wait before I start testing? I realize I can test now with the First Response Test but I don’t want to overreact.