Yep, to use AWS S3, you'll need a lock to ensure a single job at a time, or create buckets programmatically for each test. I think every team needs to decide

Yep, to use AWS S3, you'll need a lock to ensure a single job at a time, or create buckets programmatically for each test. I think every team needs to decide how much to follow the original advice, there is certainly a balance between simulating external service locally (with possible associated behavior changes) or using an external service. If you do want to run everything locally, there are servers which offer S3 API, like "minio" and "fake_s3". Probably would be very nice for localhost operation. But if you need a complex thing like Transcoder this is not going to work.