In the semiconductor industry, ATE engineers are automated test engineers who develop test programs that run on ATEs made by companies like Teradyne. People will take a microchip or several microchips, put them on a test board, load it on the ATE, and then subject them to the ATE program that the test engineer developed. The program measures specific characteristics so that you can screen out bad chips.
If you're referring to the ATE engineers in the semiconductor industry, they increasingly work in Asia.