How to start unit-test old and new code?

Question

I admit that I have almost none experience of unittesting. I did a try with DUnit a while ago but gave up because there was so many dependencies between classes in my applicatio

Answer 1

Writing unit tests for legacy code usually requires a lot of refactoring. Excellent book that covers this is Michael Feather's "Working Effectively with Legacy Code"

One additional suggestion: use a unit test coverage tool to indicate your progress in this work. I'm not sure about what the good coverage tools for Delphi code are though. I guess this would be a different question/topic.

Working Effectively with Legacy Code