Scope
Why is the test card for error not working as expected for Cybersource?
Solution
Cybersource gateway when tested with error cards for failed transactions goes through successfully.
This is because Cybersource gateway accepts all cards in the test mode and there are no transaction declined cards for Cybersource. Even the test decline cards present in our docs do not work for Cybersource.
However, as per Cybersource, you can use the zip code 46282 on the payment details page of the checkout (not the billing page) to generate a decline with any card number.