I talked to USPS and I think in the deep recesses of my mind I remember someone else mentioning this.
Since you guys developed this, no testing is required.
Just call up USPS at the number they provide on the email response to your initial application and they'll put you on the production server!. Voilà! I now can process orders all the way through. Only problem is – is $10.35 the correct amount for a 1 lb package shipped from me to me?