Jepsen is a tool used to test the linearizability of distributed systems, including MongoDB, by simulating network partitions and analyzing the consistency of the system's history. MongoDB has integrated Jepsen with its continuous integration system, Evergreen, to automate testing for linearizable reads in MongoDB 3.4. The integration involved creating a new variant of the Evergreen framework that supports Linux containers, provisioning the required environment for Jepsen, and modifying Jepsen to provide automated test runs and support for the Evergreen interface. This integration has enabled MongoDB to ensure no regressions are introduced during development and to continue testing various aspects of the system.