What would you do when you are about to add some new features to a large (and dirty) codebase which has virtually *NO* unit-testing code?

Question

Martin Fowler says that we should do refactoring before adding new features (given that the original program is not well-structured).

So we all want to refactor this

Answer 1

Let me recommend the book Working effectively with legacy code by Michael Feathers. It contains a lot of realistic examples and shows good techniques for tackling the legacy code beast.