Testing strength standards is fairly straightforward: can you lift a certain weight for a certain number of reps, or not?
However, measuring cardiovascular and aerobic function can be more complex. Of course, there's a straightforward race or time trial -- how fast can you go over a certain distance -- but this does not consider different cardiovascular energy systems, or the role of mental fortitude, for example.
Even more complex is measuring nervous system function. Do you live and work primarily in a sympathetic state (more hype, more stress, faster-paced sprint efforts), or a parasympathetic state (resting and digesting, slower aerobic efforts)? This is important to consider as it can be a window in both the effects of our training, and how we are coping with all of the other stresses present in our lives.