I would like to refactor a large legacy application originally written in VB6 and subsequently ported to .NET. In order to do this with confidence, I want to have unit tests around the existing code so I can compare before and after. What's the easiest and most effective way of doing this?
There's a book called "Working Effectively with Legacy Code" that looks like it might help me. However, it looks like it only deals with object-oriented languages and VB6 is not necessarily OO. Can this book still help me? I'm hoping someone who's read it can vouch for it.
Specifically, this application uses no classes other than the forms themselves. It accesses the db directly from the forms, and not consistently. There were several people working on this project all using their own styles with no standards whatsoever.
Final Edit: As I said, this project has been ported to VB.NET. However, it's only ported in the sense that it compiles under VS2008. All of the coding concepts are VB6.