There's a fella at Blackpool Illuminations dept. who spends all day, every day, just plugging lightbulbs into a test board to see if they work.
They used to re-use the bulbs every year which of course meant they all had to be tested again, but with modern LED technology and the banning of incandescents it's now cheaper to throw them away and start from scratch (they re-use the LEDs). They still all need testing though.