Salaams. One thing i always do to make sure an amil is genuine is by making sure the ta'weedh is written in Quran verses. If it is, then it is perfectly fine and you should not just merely 'test' it. You should have yaqeen (conviction) in it's cure. Allah swt Himself tells us that he revealed the Quran as a shifa (cure). So there can be no doubt in this. Alhamdulillah i know of people that have been very severly afflicted by ailments and with the blessing of Allah, and through the work of such ulama have found relief and cure. Whether it is related to jinns, black magic or other bodily illnesses. Remember that your primary conviction and reliance is purely upon Allah swt and the speech of Allah (the Quran). Everything else is a means, just as when we take medication, the cure is from Allah swt and the medicine is just a means. Allah swt has created this world as a place of means, where things are done through means. Hence why we have to work for rizq, take medicines (whether natural or in tablet forms) as a means for cure or anything else we want to achieve. wallahu a'alam, wassalaam.