When I was on Reddit a few months ago (Jan? Feb?) I saw two people get testing done on compounded tirz (Tirzepatide Compound subreddit) but then never again. It’s very uncommon in part because most labs test lypholized powder, not solutions. Also, since you have to give up a vial, which is usually $130+, and since using the single vial way of acquiring meds (or 3-6 months worth in a multi use vial) takes a longer time to get a stockpile, people are more reluctant to give up their meds for tests.
Before my time, there was a scandal on the subreddit about a compounding pharmacy, Ousia, which was produced in not at all sterile conditions, and people call it bathtub tirz. Most people say it still worked well, and one user said it tested clean, but all this is just hearsay from what I’ve read.