Credit card numbers are not random. In addition to bank and account number there are extra digits. a customer or a clerk hasn't made a mistake typing in the long 16 digit number. In fact even magnetic strip fail, and errors in transmission from a chip reading devices can also fail to send the correct number.

They use something called Luhn' Algorithm to detect errors. Here is a video that explains how to see if a credit card is valid.

For this lab, we will write and test the validity of a 16 digit credit card.

The practice of extreme programming starts with writing the code to test if Here is a video that explains how it works