The Alternator can be tested easily with any digital meter with DC voltage scales, set the meter to the 20 Volt DC volt scale, start the bike and hold a high idle, about 1500 RPM, the voltage at the battery posts should read about 13-13.8 volts. The battery should be in good condition and been tested for dead cells, a defective battery will affect the Alt. output readings. The #1 cause of slow crank or no crank (usually just a click sound) is the battery, these small batteries are very short lived, 2 years maybe 3 if you use a maintenance charger like Battery Tender branded chargers. Never charge a cycle battery at more than 1 AMP, it will overheat and destroy the cells. It would be easier if you just stated the problem you are having, I have 40 years experience owning all makes of motorcycles and repairing them myself Battery issues where the #1 problem on every one. Follow the link to a meter that is perfect for this type of check.
7 Function Digital Multimeter

Connect a volt meter to the battery and start the bike....should be reading above 13volts if not alternator not functioning properly.