🚧 Add broker status page

backend/tests/test_api.py

@@ -194,6 +194,51 @@ def test_system_endpoints_rbac(auditor_client):
     )
 
 
+def test_broker_status_endpoint(admin_client, auditor_client):
+    """GET /broker/status returns the $SYS snapshot (spec 33/55).
+
+    No $SYS messages are ingested in tests (no real broker), so the
+    endpoint must report available: False with all metrics None; after
+    ingesting fake $SYS messages the snapshot reflects them. Read-only:
+    the auditor role may view (spec section 9).
+    """
+    from app import metrics
+
+    metrics.reset()
+
+    empty = admin_client.get("/api/v1/broker/status")
+    assert empty.status_code == 200
+    body = empty.json()
+    assert body["available"] is False
+    assert body["version"] is None
+    assert body["clients_connected"] is None
+
+    # Ingest fake $SYS telemetry and verify the snapshot reflects it.
+    metrics.handle_sys_message("$SYS/broker/version", b"2.1.2")
+    metrics.handle_sys_message("$SYS/broker/clients/connected", b"4")
+    metrics.handle_sys_message("$SYS/broker/retained messages/count", b"7")
+    metrics.handle_sys_message("$SYS/broker/load/messages/received/1min", b"1.25")
+
+    body = admin_client.get("/api/v1/broker/status").json()
+    assert body["available"] is True
+    assert body["version"] == "2.1.2"
+    assert body["clients_connected"] == 4
+    assert body["retained_count"] == 7  # topic contains a literal space
+    assert body["load_messages_received_1min"] == 1.25
+    assert body["last_update"] is not None
+
+    # Unknown $SYS topics are ignored without breaking the snapshot.
+    metrics.handle_sys_message("$SYS/broker/something/unknown", b"x")
+    body = admin_client.get("/api/v1/broker/status").json()
+    assert body["available"] is True
+
+    # Read-only for every management role (spec section 9: auditor has
+    # read access to configuration/status).
+    assert auditor_client.get("/api/v1/broker/status").status_code == 200
+
+    metrics.reset()
+
+
 def test_role_acl_lifecycle(admin_client):
     admin_client.post("/api/v1/mqtt/roles", json={"rolename": "telemetry"})