I was wondering here, how do you guys organize your projects, in terms of functionality, scope, etc.

Do you have one project for unit tests, one project for class library code, one project for User Interface?

Or do you just divide all these into separate folders?

I was thinking that separating these by projects is easier, because your central code library is at one place, without direct references to the UserInterface (no WinForms dependencies) or the UnitTests.

Any opinions?