MongoDB 3.4.0-rc3 with v1 replication protocol and majority write concern manages to pass Jepsen testing, says jepsen.io. That is quite an achievement.
Jepsen is a framework for distributed systems verification, with fault injection. It allows reliable diagnosis of Heisenbugs in distributed systems, with a clear analysis of the conditions that lead to the fault. By this, Jepsen testing allowed for the first time systematic testing and debugging of distributed systems and the real-world implementations of the consistency protocols in them. It’s built largely on the work of Kyle Kingsbury.