Well, the speed of your autofocus depends on a variety of different factors. Lighting conditions, subject contrast, lens, focal range, af drive, af sensor type and processor speed are those I'd consider of the top of my head.
AF works slower in low light or low contrast situations because the camera has a harder time to figure out when the image is sharp. Lenses with a large focal range (like 150-600mm) need time to move the focus through that range, that's why they often have range limiters for quick focusing. Ultrasonic AF drives are generally faster and quieter than "traditional" drives. Mirrorless cameras focus using the captured image and software and need good processors to get a quick focus. DSLRs rely on specialised focus sensors.
Setting up a common test, eliminating all possible outside errors and testing a wide variety of cameras with an even wider variety of lenses seems unnecessary given that even most mid range cameras should have a pretty snappy focus these days.