> This seems an issue caused by two problems, inadequate integration testing and bugs in the original function, neither of which are your fault. I believe the

> This seems an issue caused by two problems, inadequate integration testing and bugs in the original function, neither of which are your fault. I believe the problem may be the culture. Business logic that handles sensitive things where bugs can cost a lot of money is one place where hardcore DRY and factoring everything into small functions is not such a great idea. Yes, it may be a big function, and there is an upfront overhead of having to understand it all to make a change, and there is some duplication of code, but once you understand the function you can reason locally and such bugs would be less likely.