Testing In app purchases

I am getting close to releasing my first game for iOS. I am going to use IAP to allow upgrading from the free version to the paid version. So in addition to this being my first iOS app, it is also my first one using IAP.

Could someone tell me the best way to test IAP to make sure I have covered all of the scenarios? Also, how many test accounts do I need to set up so that I can test everything?

Thanks,
Mark [import]uid: 117098 topic_id: 23560 reply_id: 323560[/import]