The core part of testing a credit card is the credit card number. A credit card number is a set of numbers and letters that uniquely identifies a credit card. Credit card numbers usually consist of 16 digits. The first 6 digits represent the identification code of the card issuing bank, the middle 9-10 digits represent the account number, and the last digit is the verification code. Some credit card numbers also contain letters or other special characters. During the process of testing credit cards, testers need to ensure that the credit card number is valid and unique. To avoid the leakage and misuse of test data, testers often use dummy credit card numbers or test credit card numbers for testing. These dummy or test credit card numbers are typically generated by specialized testing tools that guarantee their validity and uniqueness without any impact on the real credit card account.