Originally Posted by Jeff Neese

Sure they do. From Schwalbe's web site https://www.schwalbetires.com/bike_tires/tubes/all
"All tubes are inflated and stored for 24 hours in order to test for air pressure retention. Afterwards each, individual tube undergoes a careful visual inspection."

Continental also tests each tube. That's why they're more reliable, and also more expensive. You get what you pay for, especially with tubes and tires.