If you are using a sandbox it works just like a live account. The test transactions will flag a duplicate charge and deny if you order the same amount for the same address too fast.
For customer profiles, I think those actually charge $1 then reverse it. There, I think your limit would be more determined by the issuer of the card you are using. A while back I was working on a SIM integration and the owner set me up a .01 product to test, so that we could keep the site live while I worked on it.
After 70 consecutive transactions, it finally flagged a fraud altert or some such thing with my bank. It was way up in the morning so I couldn't do anything, but all you'd have to do is contact your bank. On a side note, I find it hilarious how they flag 70 cents all of the sudden, but 69, 68 cents, etc. are apparently fine. I don't know how they set the cutoff or why they would pick that amount.
