Merlin Unterfinger developed an integration test for the matsim-org/matsim-libs repository, focusing on the Railsim module’s behavior at a complex three-way rail junction. Using Java and leveraging expertise in integration testing and rail simulation, Merlin introduced the microJunctionFlat test to simulate bidirectional traffic, conflicting paths, dense schedules, and short headways. This approach validated conflict resolution and resource locking under high contention, providing a repeatable framework for future regression detection. The work expanded test coverage for critical Railsim pathways, improving reliability and reducing production risk by ensuring that high-contention scenarios are thoroughly validated within the MATSim simulation environment.