[beezee]

The time it takes to walk someone through all the use cases that need to be tested is not trivial. The reason for having a dedicated tester is so that knowledge of the system accumulates. I can't imagine how having to re-introduce your system to a new tester for every upcoming deployment could possibly be a realistic approach. In order for this to make sense I'd have to build a relationship with a freelance tester so that the same accumulation of knowledge could take place.

[cantlin]

In some circumstances "accumulation of knowledge" in a tester is exactly what you're trying to avoid. Fresh eyes can be very valuable. Amongst other reasons, this is why we don't give developers sole responsibility for testing their own work.

[andybak]

That's an interesting point but I think it highlights that there are different types of testing - even above the obvious UX vs QA distinction.

I find that really good QA testing often needs someone quite technical and even someone who has some insight into the way the code works. You have to actively think about ways the system could break. It's probably closer to the mentality of a penetration test than it is to usability testing.