If you haven't already, start by selecting 'SecPay' from the drop-down box on the Payment Setup screen, then click Save Changes. The SecPay settings will be displayed.
With your SecPay mode set to 'test', use the following test card numbers:
Visa: 4444333322221111 Visa: 4111111111111111 Mastercard: 5555555555554444 Mastercard: 5105105105105100