Aphyr didn’t test foundation himself, but the foundation team did their own Jepsen testing which they reported passing. All of this was a long time ago, before Foundation was bought by Apple and open sourced.

Now members of the original Foundation team have started Antithesis (https://antithesis.com/) to make it easier for other systems to adopt this sort of testing.

wasn't tested because: "haven't tested foundation in part because their testing appears to be waaaay more rigorous than mine."

https://web.archive.org/web/20150312112552/http://blog.found...

apparently wasn't tested because Kyle thought the internal testing was better than jepsen itself: https://abdullin.com/foundationdb-is-back/