Well it depends on what we want to find out. We would assess the needs of the sport and the athlete we worked with and then select a battery of tests that would be most suitable. For example we would not test a swimmer the same way as a gymnast, or judo player! Usually I am looking to improve performance so the tests are specific to the athletes sport and maybe on a certain aspect of their fitness.
If we were just testing generally, for say health screening or for talent Identification we may do a whole range of tests looking at all aspects of fitness. There are several areas can you name them?
Endurance is one. We could test this doing a bleep test, or in the lab we might use a face mask and a treadmill and measure how much oxygen the subject can use and what waste products (like lactate) they produce in their blood.
Also think what might be needed to be fit for your sport, or a sport you like watching.
Here is a link to a common test we do, in our lab with myself leading it.