To access the MasterCard Payment Gateway test simulator, ensure gateway mode is set to TEST. The test simulator is configured to generate predictable results based on the transaction request and card details you supply.
You can trigger specific transaction responses, for example the MasterCard Payment Gateway Response Code and Card Security Code validation, as well as Address Verification response codes. You can also test features like Risk Management and Wallet functionality.
Details of test cards can be found here.
Successful Authorization including 3-D Secure
Create an Invoice & Capture Online
Submit a full refund for a invoiced order
Submit a partial refund for an invoiced order
Refund, Capture, Void via Merchant Administration