I thought that was actually one of the points is that the purpose of the fitness test is at least as varied as the test themselves.

If we just want to focus on individual progress, a test you can do yourself, to measure benchmarks I would change a couple things. The mental barrier thing is less important. The beep test is just too long boring and I lose count too easily. Many of the tests used for team selection or done in groups are just not appropriate.

I would add a bit to Hamish's list keeping all his points, the test should be simple and repeatable, basically it could be a normal (swim, unders, kick, under/over) workout set of ~1000 to 2000 m. With a set warm up or pre-set done every time, with the same rest times and measurable goal times. Also for this to truly be suitable and give you the information you want, a Heart Rate monitor is nearly essential. there are times you may feel like you didn't do very well, and maybe times didn't show any improvement, but your HR recovery can show you that you are improving.