When should I use specs for Rails application and when Cucumber (former rspec-stories)? I know how both work and actively use specs, of course. But it still feels weird to use Cucumber. My current view on this, is that it's convenient to use Cucumber when you're implementing application for the client and do not understand how the whole system is supposed to work yet.
But what if I'm doing my own project? For most of the time, I know how the parts of the system interact. All I need to do is to write a bunch of unit-tests. What are the possible situations when I would need Cucumber then?
And, as a corresponding second question: do I have to write specs if I write Cucumber stories? Wouldn't it be double-testing of the same thing?