A certification exam wouldn’t survive a disparate impact challenge. Google stopped asking for SAT/ACT scores long before universities did. And long before that (according to my father, who actually used them), telegram companies had to stop giving spelling tests to telegraph operator applicants. Add to that difficulties with preventing cheating during a pandemic, and I see no alternative to rolling your own live examination. (Not that I’m defending the often dumb choice of trick tree recursion coding problems; I didn’t learn a lot about a candidate by watching him not get the trick.)