How to test for chemicals on weed?

hey guys, I usually smoke medical so I trust where it comes from (CA) but my friends picked up from a really sketchy guy yesterday that they don't usually pick up from and when we got the weed it smelled overly fruity, unbelievably fruity to where this couldn't actually be just from the plant, it didn't even smell like weed anymore just this fruity substance and it had a really chemically after burn smell to it, anyways we smoked it and two things I noticed that are signs of sprayed weed was that the weed did not burn at all, we had to keep the lighter on the joint just to get it to go which is really odd for regular weed. it was like it physically would not burn by itself and also the ash was really weird, I know it's a tell tale sign for the ash to be burning weirdly and usually the ash is soft and blackish white and stays together in a tube pretty well until you ash it in the ashtray, anyways the weed would burn to semi black and then just flake out and fall apart in these large chunks, never even got to white. the smoke was also really harsh and gross, not typical weed "harsh" though. I know some people worry it's laced or some shit, I know it's not PCP or any drug, it's 2017 and no one wastes money tainting your weed with more drugs (it also didn't give me any extra effects or anything like that) but the fact of all this kinda made me wonder what the fuck we got and so I'm wondering if there's any chemicals or substances people have sprayed on weed or used during the grow in the past to give it a very strong artificial fruity smell and if there's any way I can test for something odd in my weed.