Thats going to be hard to measure as most home multimeters will not be able to measure the voltage which for some coils may exceed 40,000 volts
If you suspect trouble with your coil the usual way to test them is measure the resistance and check the continuity.
for the low tension side its usually between 3-5 ohms
and the high tension side between 10,000-15,000 ohms
If you did only want to know the output voltage you could have a guess using measuring the resistances to calculate the ratio of the windings and then measure the input voltage and multiply it by the transformer ratio
