[dpifke]

You elided the part where TFA claims you can't test "unconventional email formats" via test orders. The full quote is:

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.

[Groxx]

Anyone who has used these kinds of systems will have encountered tons of cases where those test systems weren't enough, so they use real purchases too

The test systems are broadly good and worth using, but no. Everyone uses real purchases too.