Unless you consent to this as a precautionary measure to your treatment.
no, doctors can make it as part of the consent to be on that kind of treatment, through a contract between the patient and themselves. basically any drugs of addiction/abuse like amphets, benzos and narcotics, doctors (have the power and) can now enforce a drawn up (signed by you, the patient) contract, or verbally (as is with mine).
if you want to continue the treatment and remain with that doctor, read and sign his contract if you agree. your other option is seek out an alternative doctor who mightn't ask for a contract between the two of you. it's that simple.
I know there are many pain clinics out there who test patients that display drug seeking behavior, but if you are over the age of consent, have been taking them regularly and not asking for early refills, just ask him what the reason could be; who knows, might bring the two of you together.
And no; I'm at 120 x 15mg XR every 28 days and I never have been tested for years. Only have from the pain management clinic really.
not only is it for drug seeking behaviour, but it's to make sure patients are taking their medication and not selling it. patients(especially methadone patients around here) will get blood tests done to check their plasma levels are where they should be as well. it stops patients from being illegitimate, and rightly so.
anyway, OP, talk it through with your doctor and if you're comfortable and agree to the terms of his contract then do it and keep seeing them for treatment (best idea, imo, esp since you've been seeing him for 3 yrs already. you've already built up that relationship and trust.) or seek out another doctor.
i'm sorry but i'm going to close this thread now as it's been answered well and it comes under the part of self serving threads. we get this question in here a lot. anything further, shoot me a PM and i'll help you out.