I'm reading Osherove's "The Art of Unit Testing," and though I've not yet seen him say anything about performance testing, two thoughts still cross my mind:

• Performance tests generally can't be unit tests, because performance tests generally need to run for long periods of time.
• Performance tests generally can't be unit tests, because performance issues too often manifest at an integration or system level (or at least the logic of a single unit test needed to re-create the performance of the integration environment would be too involved to be a unit test).

Particularly for the first reason stated above, I doubt it makes sense for performance tests to be handled by a unit testing framework (such as NUnit).

My question is: do my findings / leanings correspond with the thoughts of the community?