The board fab I currently use is organized through Seeed Studio, and they do visual inspection but not electrical testing. They provide a service of full impedance control, for a fee. With the amount of boards I have them make, and the relatively low complexity of the boards, the cost has been too high for the LiNC80/Z50Bus series of products.
So far, I've spotted two boards with defects, and gotten Dillions report here of one that slipped through my fingers, across all PCB's I've had from Seeedstudios. I think I'm getting close to 500 boards from them, across all my projects and products. I am looking at testing other board houses, and at the same time I will gladly speak well of Seeed (as I have on my sporadically updated personal blog, where the "road to the sbc1" is documented, see
http://defcon.no/tag/homebrew ).
The board house I currently use work from Gerbers only, unlike EasyEDA/JLCPCB who also have the schematic. Trying to do electrical check based on the Gerber files alone would require significant setup to be able to do an electrical test, and I suppose that's why Seeed charges a significant fee for impedance testing, even after requiring the customer provides the impedance control information. Personally, I would be surprised if JLCPCB actually do any testing at all, considering the amount of setup and labor needed.