Continuous improvement: Is it possible to specify the tests in advance?

I am used to "old fashioned" waterfall development cycles. For a project, continuous integration seems to better fit our need.

In waterfall, you have to specify the tests you will to implement in advance.

My questions:

• What is the usual way with continuous integration development cycles regarding specification?
• If you don't specify the tests, can you imagine a way to specify them in advance?

Many thanks for your help.