Any stress-tests done after 2015?
The 2015 stress test aimed to hit 200MB of backlogged tx, they only hit 15MB as reported by coindesk.

Blockchain.info reports that the backlog of tx hit 120MB May 16th 2017. It's mostly been above 20MB for the last 60 days as of this post.

How big of a stress test is big enough for you?