It’s quite normal to think that each line of code written by you is perfectly good. Unfortunately, I have to upset you – you’re wrong. Every developer makes bugs, but not all developers know how to prevent them. I think there’s no need to explain how important it is to create safe and bug-free software in payment processing. Apparently, it seems that good solutions that help to avoid bugs, seem to use the unittest framework – a module that’s available for most popular programming languages like PHP, Python, Java, C#, C++.