When testing a new AR build, I'll load a single round into a magazine, slap it home, release the bolt, and fire the single round. If it locks back then I know the "stroke" is fine. If it doesn't lock back, then I know I have a cycling issue. If it fails to lock back, I would go ahead and try a different magazine. If we fail again to lock back, I can be reasonably confident that the issue is short stroking. (It should lock back weather you have a good extraction or not.)
If it extracts and expells the spent casing, then I know the extractor/ejector system is working as it should.
Next, I'll load 2-3 rounds. If they cycle then I'm good as far as the mag lips go. Next is to load a full magazine.