Yes, you can refuse testing that you recognize as superfluous, but, well, I'm not a doctor, they are. More often it goes the other way - eg most of the time I request a test that WebMD has convinced me will tell me that I don't have, well, cancer, and doctors are willing to oblige, but only at my behest. Serina Williams famously almost died because her doctor didn't think a test was warranted. Her advocate had to lobby the doctor to run a test which led to a diagnosis that saved her life. (A combination of racism and sexism certainly played a part there.)

The problem is that the profit motive is hard to deny, simply because healthcare is run as a profit seeking venture, which makes money on the difference between the cost of running a test and the price a patient's insurance will pay. Pharmaceutical companies bribing doctors to prescribe specific medication doesn't help.