Both wallets charge directly through ArtsPay's purchase API instead of the Hosted Payment Page. Apple Pay only renders in Safari, over HTTPS, on a domain registered with Apple (see README). Google Pay needs a browser the Google Pay API supports and a Google account with a saved card.
Sandbox responses are cent-based: the cents of the amount become the simulated response
code, e.g. 10.05 declines with code 05, 10.00
approves. See the Apple Pay /
Google Pay guides' Testing
sections.