No drug testing questions aloud, but I literally deal with this myself. Basically unless they find the signs of use before it coverts into Morphine it will look just like Morphine. That being said I wouldn't recommend cheating the test and will not give you the time estimate of how long anything more than morphine would be visible. Plus there could be drug tests I don't know of that can test somehow for heroin use even after it coverts to Morphine.