The checkout process attempts to validate a credit card when it is first entered. This includes things like expiration date as well as a mod check against the number. All credit card numbers pass a particular mathematical algorithm that validates them as real numbers. So, in order to actually complete the checkout process a credit card number that passes this test must be supplied. ATG Consumer Commerce does not accept random 16-digit numbers. You can use one of the following credit card numbers for testing:
Visa: 4111111111111111
MasterCard: 5555555555554444
American Express: 378282246310005
Discover: 6011111111111117
The expiration date for all cards can be any date in the future.