In this directory are 5 files:
CreditCard.rb: Class file for storing information about a credit card number with methods for determining its validity.
CreditCardCLI.rb: Comamnd line interface program. Run this file, with 'ruby CreditCardCLI.rb' via the command line, to enter credit card numbers and see their validity.
CreditCardTest.rb: Unit tests. Run this file, with 'ruby CreditCardTest.rb' via the command line, to test the code with the provided test data.
CreditCardValidator.rb: Module file with helper validation methods for the CreditCard class.
ReadMe.txt: This file.

Although this task could have been accomplished in much fewer lines, I chose to objectify the process for the purpose of reusablity and also to demonstrate my skills and knowledge in aspects of the development process.