What this simulator helps test
SPX works as an MQTT simulator for device telemetry, command topics, retained messages, reconnect behavior, and automation flows. The simulator is tied to a running digital twin, so MQTT messages can reflect meaningful device state instead of static test payloads.
Why SPX
SPX combines protocol behavior with model state, scenarios, and runtime observability. That makes MQTT testing useful for integration teams that need repeatable topic behavior before physical devices or cloud-connected fleets are available.