How the Einstein photoelectric equation was tested?

It was Robert Millikan who tested the Einstein photoelectric equation. He first calculated the kinetic energy gained by the emitted electrons for a number of frequencies by applying an opposing potential and finding the value at which the photoelectric current stops. Knowing the values of γ and γ₀, the value of h was calculated from the Einstein photoelectric equation was calculated and it came out to be 6.570X10^-34 which is same as from experiments performed on black body radiations.