Is it easy to test human Flicker Fusion Threshold?
Flicker-fusion rates are very easy to test in humans: you provide a flickering light-source, set it to flicker at different speeds, and get the people to tell you whether the light is flickering or constant. This paper (from 1952) achieved a flickering light by putting a rotating disc with holes in it in front of a projected light source. A more modern testing unit is demonstrated here.

The human flicker-fusion rate does not appear to be a constant. In addition to being influenced by attributes of the light source (such as its wavelength, how much the brightness changes, etc), it also appears to be influenced by factors such as stress and fatigue (pdf).