Test Samples:

Correct Credit Card Numbers:

• Visa: 4111111111111111
• Mastercard: 5555555555554444
• American Express: 378282246310005

Incorrect Credit Card Numbers:

• Invalid length: 123456789012345
• Invalid prefix: 1234567890123456
• Invalid Luhn check: 4111111111111112

Luhn Algorithm:

Here is an image explaining the Luhn algorithm: