Removing tightly coupled code

Question

Forgive me if this is a dupe but I couldn't find anything that hit this exact question.

I'm working with a legacy application that is very tightly coupled. We are pulling out some of the major functionality because we will be getting that functionality from an external service.

What is the best way to begin removing the now unused code? Should I just start at the extreme base, remove, and refactor my way up the stack? During lunch I'm going to go take a look at Working Effectively with Legacy Code.

Answer 1

If you can, and it makes sense in your problem domain, I would try to, during development, try and keep the legacy code functioning in parallel with the new API. And use the results from the legacy API to cross check that the new API is working as expected.