Don’t know what type of measuring set-up you’re thinking of, but if there’s a few microns of real gold all around it will probably pass the conductivity test at low amperage/low voltage (”low” meaning well below kilo Volts and kilo Amps).
There are other simple tests. Pure gold is (very) soft, tungstene is hard, the difference can be felt and heard when choking the bar. Thermal conductivity differ too => heat at one end and observe the difference in the temperature rise rate at the other end). Thermal capacity differ also => put in boiling water or in ice and measure the time it takes to get back to temperature.