This is a very long method, consider seeing if you can break it up or generalize some parts so it's a bit shorter.  This will also help if in the future we want to add to the test but change some small part of how ``run_once()`` works - then we can just override one method instead of all of the code.  Also, if some method is used a lot, we may consider moving it into the dockertest package so all tests can benefit.  It also helps the code be easy to read, since you don't have many many levels of nesting.  Does that make sense?