Build a coverage matrix for a networked-game state machine that exercises connect / authority-handoff / disconnect / reconnect / host-migration paths across Unity Netcode for GameObjects, Unreal Engine replication, and Mirror Networking. Workflow: enumerate the engine's connection states + ownership states + replicated-property update rules, cross them against latency / loss / out-of-order packet injection, encode each combination as a test fixture, and emit a go / no-go gate. Use before submitting a multiplayer title to platform cert - Microsoft's cert guide lists 'Multiplayer does not work as expected' as one of the most common Hold reasons, and Xbox XR-067 (MPSD session state) is failed by uncovered state-machine paths.