The Sandbox testing suite - everything you need to exercise your integration before real customers do.
In Sandbox, every part of the payment pipeline you don't control is replaced by a testable stand-in: real cards become test cards, and the bank's 3DS challenge page becomes the 3DS simulator. Walk the checkout flows as your customers will experience them, then finish with the core test scenarios - order, refund, and webhook - that every backend should handle.
Everything here assumes your integration is pointed at Sandbox.
Test cards
The full list of Sandbox test cards and their outcomes
3DS simulator
How the simulated 3DS challenge page works and how to complete or automate it
Test payment flows
Walk through checkout flows in Sandbox - payment links, Revolut Pay, and Google Pay
Sandbox test scenarios
The order, refund, and webhook scenarios every backend should handle