geoff wrote:
You think that they really waste time and effort doing something like
that ?

costs more than the monetary value of the resistors

Depends. It may be worthwhile to have an automated tester as part of the
production line than sorts them into different bins based on value. After
all, the production process requires more work than that step (making carbon
rods/wirewinding, soldering on leads, casing in ceramic/epoxy, painting,
colour coding, railing). You probably want some kind of tester anyway to
reject those that are open circuit or way off tolerance.

Theo