What Is the Main Benefit of Writing Test Cases?

Blogger Pawel Brodzinski writes in his post today, test cases for application functionality are the same as unit tests for application code. Except of one thing: it is way harder to write good and complete list of test cases. You may safely assume that’s impossible. This means the main value of test cases isn’t in covering full application functionality because you simply won’t achieve that, no matter how hard you try.

Read the rest of his post here.

What do you think are the benefits of writing test cases with project management? Do they waste time or save time? We'd like to hear your thoughts.