If you are talking about IC’s, yes. Manufacturers (not distributors) normally test 100% of the IC’s as part of the production process. As far as I know, this applies regardless of country of manufacture. Distributors don’t test anything. That is not their job.
Manufacturers may not test 100% of the features in a product, but they will test the product in some fashion. At a minimum, they will test each component on the wafer and discard bad components prior to packaging. (Wafer sort). The extent of the post-packaging test probably varies depending on the complexity of the product, etc.
I think if electronics products factories test incoming electronic components prior to PCB assembly, they must be very faithful. You might have an acceptance test for things like speakers or LCD displays, but not for the components soldered to the PCB. If something like that is required, you would probably modify the design to exclude the troublesome part, or work with the manufacturer to improve outgoing quality.
One thing you should DEFINITELY NOT do in China is buy major brand parts through gray market channels. There is a lot of fraud and counterfeiting going on. If you buy major brands, buy through authorized distributors only.
#PCB Assembly #PCB Testing