I work for the company Fitech, we are the people that devise these fitness tests and record the information.
If anybody has any questions or would like some advice on fitness assessment I would be happy to answer your questions. Please email me at r.pitkin@fitech.co.uk.
To answer some of your questions, the chester step test is a very good indication of a person fitness. Some people may fail the test, this is only because they are not aerobically fit.
To gain entry into the fire service you have to reach a minimum VO2 max of 40ml/kg/min which is tested by the chester step test. This level is well above a normal persons fitness, to reach this level you must be fit, a good guide to how fit you must be would equate to being able to run a mile in under 7 minutes.
This test was selected as it mimics the job stresses a firefighter may endure, ie climbing steps or ladders.
Regards
Robin Pitkin
BSc, Msc (Sports Science)