@Tahli I never had any of our embryo's PGD tested as we couldn't afford it at the time. But I do know from some of my other BH Buddies who have had it done that they seem to mainly embryo bank before testing..which in all likelihood would mean doing a couple of stim Cycles first to get them.
Not everyone does it that way. Some test per stim Cycle depending on the amount of embryo's that they have. What day do they test at your Clinic Luv?? Most FC's have a maximum amount of embryo's they'll let you keep in the freezer to test, so you'd have to check with your FS/Clinic what their rules are.
I don't think there's a minimum as such, but, if for eg, your Clinic biopsies them on Day 5, you might only have a couple left at that stage that are suitable to be tested. Most women would bank those (if that's allowed at your FC) and stim again to get some more before sending them all of to get tested. Some embryo's aren't suitable to be biopsied, so there's that to consider too.
Also, so FC's charge per embryo to be tested, some for the testing itself as a whole. Some Ladies do put a fresh untested embryo in and hope for the best, some don't and just do a freeze all and go on to the next stim Cycle. Best to check with your FS about that Luv and see what he/she recommends. Will put a shout out shortly to some of my friends here who've had it done to see if they can shed a bit more light, ok Luv??