There are two kinds of tests; immunoassay IA) which is less accurate with lots of false positives and false negatives, and there is chromatography which is very accurate and definitive. On and IA test, it just tests for “opiates” and moderate to high doses of hydrocodone or oxycodone can come back positive for “opiates” without distinguishing between the two.  Chromatography testing will identify the specific drug.