MQTTnet 5 does not throw on an unsuccessful CONNACK — it returns the reason in
MqttClientConnectResult.ResultCode and v5 removed v4's ThrowOnNonSuccessfulConnectResponse,
so ConnectCoreAsync's unconditional SetState(Connected) sealed a wrong-password deployment
green: DriverState.Healthy / HostState.Running on a session that never authenticated.
Caught by the Task-13 Mosquitto fixture; 240 offline tests missed it.
ConnectCoreAsync now inspects the CONNACK and raises MqttConnectRejectedException.
Credentials/identity/protocol/Last-Will refusals are unrecoverable and set Faulted, which
stops the reconnect supervisor; transient refusals (ServerUnavailable, ServerBusy,
QuotaExceeded, UseAnotherServer, ConnectionRateExceeded, and anything unrecognised) stay
Reconnecting under backoff. MqttDriverProbe now shares the rejection wording, so the
AdminUI Test-connect button and the running driver can no longer disagree.
Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW
Adds the MQTT driver integration-test project: an eclipse-mosquitto fixture running
auth AND TLS (allow_anonymous false on both listeners), a mosquitto_pub-based JSON
publisher emitting retained messages, a cert/password generator script whose output is
gitignored, and a live suite gated on MQTT_FIXTURE_ENDPOINT that skips clean offline.
The fixture is never anonymous by design: an anonymous broker would let the driver's
TLS/CA-pin and auth paths go untested, and those fail silently. The CA-pin leg carries
its own falsifiability control (a foreign CA generated in-process must be rejected).
Live gate on 10.100.0.35: 7/7 passed. It found a driver defect, reported not fixed
here (src/ is out of this task's scope): MqttConnection.ConnectAsync RETURNS NORMALLY
when Mosquitto rejects a CONNECT as not-authorized -- MQTTnet 5 does not throw on an
unsuccessful CONNACK, so a wrong broker password yields DriverState.Healthy from
InitializeAsync. The auth-negative test therefore asserts the invariant that holds
either way (no session is ever established) and documents the finding.
Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW
Joseph Doherty