Cannabis is more regulated than food crops are. If any labs are lying about their test results that is a different issue. Remember don't do the crime if you cant do the time.
Protection for the consumer has traditionally been lacking , a quick glance at all the effort put into killing Senator Warren's recent effort at consumer protection is a decent illustration of how things actually are here.
If one would like an example more directly related to cannabis, then I sadly offer as an example, the embarrassment around the pens.
Each time I have seen a discussion of testing, it is never long before one sees mention of the various methods of how to scam, modify, or get around such testing are brought forward.
I see it as being part of the human condition, and find that for me, it results in a greater sense of appreciation for the integrity of the individuals with whom I have the good fortunate of being able to deal with.