When should I test?

Hey ladies. I need a little advice. I'm CD 21 today (Monday). I think I'm 6 DPO. Not 100% sure when I ovulated. AF due next Tuesday. The question is: when should I take a hpt? We're going to a big party on Saturday (DH's work is throwing a big bash), so I plan to test that mornjng for sure. I'll be CD 26/ 11 DPO. Do you think I have any chance of seeing a BFP on Saturday if I am pregnant? Any point in testing before then?