This is a test of commonsense. Complete the next sentence:

How to test led lights 
Purchase a digital multimeter that can take diode readings. 
Basic multimeters measure just amps, volts, and ohms. To test led lights you will need a multimeter with a diode setting.
Check online or at your local hardware store for mid-to-high-range multimeters, which are more likely to have this feature than inexpensive models. A decent mid-range multimeter will likely cost between $50-100 usd.