how do you test the battery

Take it to a parts store they will charge and test it for you. If it is only 2 years old, the problem may be in the recharging of the battery such as the alternator.

Also a battery depreciates in value. If you pull the warrenty and return it they will depreciate the value of the battery for the difference of cost on a new one.

Maybe your batter doesn't have enough "cranking amps" required to start the car.