Credit Card Validator

This repository is a sample of a credit card validator written in Java.

Thoughts and decision-making process

• First thing after reading the problem is to establish a comprehensive test suite.
• Break down the problem into checking for length, starting number and luhn algorithm.
• Should have classes that allow extending to new rules and keep to SOLID principles. Created rule interface that is first used for the length rule
• Used the length rule in an Amex rule as a first try of the rule pattern.
• Instead of making a rule for each card, have a generic one that takes in allowed lengths, allowed start values and the enum card type for those combinations.

Any issues you ran into

• IDE messing up my gradle file :(

Any assumptions you made

• Build file is needed to have consistent rules for compilation (used Gradle)
• Do not need to create API for a simple problem
• Do not need console input/output and test cases would be enough

Anything else you feel is relevant & would add further value

• Should align the test to practical daily task of a developer, more emphasis on maintainability, test driven development.