The reason why this is so important is that you can create tests specifically based on your clients goals:
• If you have a runner, put them through a 1 mile test or 5k periodically.
• If you have someone preparing to become a police officer, put them through a pushup, pull-up, 1.5 mile test.
• If you have someone that wants to increase their max strength, track their max bench, deadlift and squat.
The important thing is that this information become intrinsically valuable to the client. Most people don't write down their workouts in the gym, so if you have a platform that tracks the clients' progress over time, they will pay you for it!