He will also need a volt meter and an adjustable voltage source as the meter places a resistor in series with the load and actually measures the voltage drop across the resistor. The volt meter allows the OP to bring the voltage to what it should be and the adjustable voltage source will facilitate that adjustment.
I use a scope probe until the current gets low then a variation of what I described above. It gets very tricky when in the low uA range. And of course there is temperature to deal with. The easiest is to believe the data sheet as it is generally a guaranteed parameter.