Based on the repository's commit message style and the changes in the diff, here's an appropriate commit message:

```
feat: add websocket tests, PoA metrics, marketplace endpoints, and enhanced observability

- Add comprehensive websocket tests for blocks and transactions streams including multi-subscriber and high-volume scenarios
- Extend PoA consensus with per-proposer block metrics and rotation tracking
- Add latest block interval gauge and RPC error spike alerting
- Enhance mock coordinator

apps/blockchain-node/tests/test_observability_dashboards.py

@@ -0,0 +1,39 @@
+"""Tests for the observability dashboard helpers."""
+
+from __future__ import annotations
+
+import json
+from pathlib import Path
+
+from aitbc_chain.observability.dashboards import generate_default_dashboards
+from aitbc_chain.observability import exporters
+
+
+def test_generate_default_dashboards_creates_files(tmp_path: Path) -> None:
+    output_dir = tmp_path / "dashboards"
+
+    generate_default_dashboards(output_dir, datasource_uid="prometheus")
+
+    expected_files = {
+        "blockchain-node-overview.json",
+        "coordinator-overview.json",
+    }
+    actual_files = {path.name for path in output_dir.glob("*.json")}
+
+    assert actual_files == expected_files
+
+    for file_path in output_dir.glob("*.json"):
+        with file_path.open("r", encoding="utf-8") as handle:
+            payload = json.load(handle)
+
+        assert payload["uid"] in {"aitbc-coordinator", "aitbc-node"}
+        assert payload["title"].startswith("AITBC")
+        assert payload["panels"], "Dashboard should contain at least one panel"
+
+
+def test_register_exporters_tracks_names() -> None:
+    exporters.REGISTERED_EXPORTERS.clear()
+
+    exporters.register_exporters(["prometheus", "loki"])
+
+    assert exporters.REGISTERED_EXPORTERS == ["prometheus", "loki"]