@xarina_onlyme a digital multimeter would be the best, but if you don't have one, a LED with a series current limiting resistor can be placed so it is powered by the 9 volt battery.
Once it is there, it will glow.
Now run your servos, you will very probably see the LED dim significantly, and recover once you've stopped running the servos, but maybe not then be as bright.
After a very short time compared to the cost of that battery, it won't even make the LED glow.
You need voltage, but you need the voltage source to be capable of delivering current. Two servos might take nearly one ampere of current, which that battery was never meant to be used for, and if it ever delivers that current, it won't do for very long.
a7