Years ago I read an article called 'the cascade effect' It was about people having medical investigations as a result of which further tests were indicated and as the tests got more complicated and the person may experience side effects from the tests themselves.

If you are asked to undergo some tests make sure you really understand the pros and cons of doing so. Look on the internet too to find out how effective the test is in diagnosing something and if there is a positive result does that mean you have to proceed to a more invasive test.
I am not saying 'don't have a test' just be really clear why and for what it is being suggested.

I'm writing this because I've just jumped off a cascade of tests which were getting more and more complicated when I suddenly thought to myself 'why am I agreeing to all this when I don't understand why I need these tests?'

Many times I suspect further investigations are suggested because of the doctor's concern about litigation. So if you decide to refuse a suggested investigation you do need to discuss the pros and cons thoroughly so you come to an informed decision!