The multi-stage fitness test, also known as the bleep test, beep test, pacer test, Leger-test or 20-m shuttle run test, is used by sports coaches and trainers to estimate an athlete's VO2 max (maximum oxygen uptake). The test is especially useful for players of sports like squash, rugby, football (soccer), hockey, netball, handball, tennis and many other sports; employed by many international sporting teams as an accurate test of Cardiovascular fitness, one of the all-important "Components of Fitness". This test is also part of the FITNESSGRAM physical fitness test to measure cardiorespiratory fitness. The test was created by Luc Leger, University of Montreal published in 1983, "A Maximal Multistage 20m Shuttle Run Test to predict VO2 Max", and was re-published in the European Journal of Applied Physiology (vol 49 pp 1–12) in 1988 in its present form with 1 min stages under the name "Multistage 20-m shuttle run test for aerobic fitness". Result equivalences between slightly modified versions are well explained by Tomkinson et al. in 2003.
Good luck, have fun.