Faulty iPhone 4S battery - how can I test a battery to measure its integrity?

I bought an iPhone 4S two months ago. In the last couple of days I've perceived an average battery life of 12 to 18 hours with a light usage of the phone throughout the day.

I've followed every tip for battery preservation such as turning off Location services, I don't use Siri, I only download e-mails manually to the phone (no push or notifications), I set the auto brightness on, I try to keep only a few important applications running in background.

I would like to visit my carrier's technicians in order to get a replacement, but I would prefer to run some tests first to make sure that something's wrong with the battery.

Any suggestions?

I have always liked to test a battery by running the device until it shuts down and powers off.

When you connect it to the standard wall charger, it should take between 2 and 4 hours to charge. If your battery is done charging in an hour to 1:30, then it's not really getting the intended amount of current and should be replaced.

Similarly, if it won't charge fully (or very much close to full) in less than 4 hours - something also is amiss either with the charging, measuring or battery itself.

By timing the charge time, you eliminate any background task, GPS, WiFi drain, etc.. and just can see the time it takes a fixed amount of current to enter the battery and be stored chemically.