>If you don't accept that concept

Nobody anywhere in the world disputes that unit tests should surround a unit.

>IMHO, the sizing of components is context, language, and team dependent. But it really doesn't matter

Yeah, thats the attitude that will trip you up.

The process you use to determine the borders which you will couple to your test - i.e what constitutes a "unit" to be tested is critically important and nonobvious.