In the testing literature, the term load testing is usually defined as the process of exercising the system under test by feeding it the largest tasks it can operate with. Load testing is sometimes called volume testing, or longevity/endurance testing.
#1 Best Method: Caffeine. Drinking caffeine will help you stay awake while driving in a few ways. The first benefit is that caffeine is a short-term diuretic. This means it will make you want to go to the bathroom. Feeling uncomfortable is a benefit when trying to stay awake while driving and it will force you to make stops to go to the bathroom. Staying alive is worth the few minutes needed for the stops. Another unrealized benefit is the action of picking up the cup repeatedly.
Here's what you need to do: Hold down the sleep/wake button (on older models it's on the top of the phone. On the iPhone 6 series and newer, it's on the right side) until the power-off slider appears on the screen. Let go of the sleep/wake button. Move the power-off slider from left to right.