[olefoo]

While you can always find the degenerate case; it is somewhat of a strawman.

I personally don't get too hung up on whether a given test is a unit test, a system test or an integration test. For any reasonably sized project you're eventually going to have all of those. And sometimes something that was a unit test will suddenly become a test that crosses multiple units as requirements change and as dependencies get added to the project.

The viewpoint I take is that tests are an integral part of the software, they may not be part of the final delivered artifact but they are part of what defines the software.

You should be thinking as much about how to test that your code is doing what it should as to how to make it do so in the first place. If you do that you will have a far better understanding of the intent of any given piece of code and you will have done half the work of debugging before you write the bugs.