Well there is only 1 ultimate fitness test. The Ironman Triathlon.

In the Ironman, the swimming portion is 2.4 miles, the biking portion is 112 miles, and the running portion is a full marathon, 26.2 miles. This is an intense and extremely challenging event which many participants do not finish. Held in the warm climate of Hawaii, the Ironman triathlons can be not only a test of training, but also a test of one's own determination.

If you can do that your extremely fit

Ultimate Fitness - The Ironman Triathlon