I agree with oldturkey03. The basic way of testing a battery is to look for the positive and negative terminals. Then use the probes of a voltmeter or a multimeter to connect with the right terminals. Grounding a resistor is needed to give a small load to the battery that will help you test it. If your device don’t provide a result, it means the battery is dead or your doing it wrong. Here is the resource where this website provides more.