You can use test mode without having to be whitelisted.
What is test mode (sandbox)?
Test mode accounts run on a staging environment and use the testnet blockchain. It enables you to confirm that your integration works correctly, and simulate transactions without moving any real money.
Test mode accounts are separated from merchant mainnet accounts, so when you are ready to create a merchant mainnet account, you will have to register for another account. Please contact [email protected] to get whitelisted to go mainnet when you're ready!
Where can I get testnet tokens to use test mode (sandbox)?