I don't know the first thing about Shopify, but perhaps you can create a free "test" item so you don't actually need to make a credit card transaction.
Shopify doesn’t provide a way to test unconventional email formats without actually placing real orders, so I did my customary dance of order-refund, order-refund, order-refund. My credit card is going to get locked one of these days.
The person who wrote the above knows a lot about Shopify, so if you're going to contradict them, it'd be nice to point to some evidence as to why you think they're wrong.
The test systems are broadly good and worth using, but no. Everyone uses real purchases too.