Updating CreditCardNumberValidator isValid methods to use the getPrefix and getSize methods that I wrote earlier. Update test class with a few more cases that should pass and are now failing.
Building out test suite (adding additional use-cases that exposed a bugs in both the even and odd-summing functions). Bug fixes to even and odd-summing functions.
Adding test code for even and odd-summing methods. Stubbed golden-path validation test.