testing and assessment for obese clients

It depends
There are many people who are classified as obese who are extremely mobile and active and then there are those who are morbidly obese and are extremely immobile

My best suggestion would be to ask yourself why?
Do you HAVE to measure? It’s no secret that the person is obese and the goal is to lose weight in order to become healthy. Assessments can be very humiliating for them.