Below you’ll find links to test credit cards for some of the most popular Magento payment providers
Sagepay
http://www.sagepay.co.uk/support/12/36/test-card-details-for-your-test-transactions
Paypal
http://www.paypalobjects.com/en_US/vhelp/paypalmanager_help/credit_card_numbers.htm
Authorize.net
http://rpmware.com/support/customers-&-orders/questions/test-credit-card-numbers
Worldpay
http://support.worldpay.com/support/kb/bg/testandgolive/tgl5103.html
Cardsave