test: add tests for status WebSocket and scheduler

- test_status.py: 8 tests covering WS auth rejection/acceptance, broadcast_status (dead connection removal, no response_time, no connections), broadcast_scan_update
- test_scheduler.py: 9 tests covering _load_interval variants, _run_status_checks DB update/last_seen/error handling, start/stop lifecycle
- scheduler.py: reinitialize AsyncIOScheduler on each start() to avoid stale event loop across test restarts

backend/tests/test_status.py

@@ -0,0 +1,148 @@
+"""Tests for WebSocket status endpoint and broadcast helpers."""
+import json
+
+import pytest
+from fastapi.testclient import TestClient
+from starlette.websockets import WebSocketDisconnect
+
+from app.api.routes.status import _connections, broadcast_scan_update, broadcast_status
+from app.main import app
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+def _make_token() -> str:
+    from app.core.security import create_access_token
+    return create_access_token("admin")
+
+
+# ---------------------------------------------------------------------------
+# WebSocket authentication
+# ---------------------------------------------------------------------------
+
+def test_websocket_rejected_without_token():
+    """Connection with no token must be closed before being accepted."""
+    with TestClient(app) as client, pytest.raises(WebSocketDisconnect), client.websocket_connect("/api/v1/status/ws/status"):
+        pass
+
+
+def test_websocket_rejected_with_invalid_token():
+    """Connection with a garbage token must be closed."""
+    with TestClient(app) as client, pytest.raises(WebSocketDisconnect), client.websocket_connect("/api/v1/status/ws/status?token=not-a-valid-jwt"):
+        pass
+
+
+def test_websocket_accepted_with_valid_token():
+    """Connection with a valid JWT must be accepted and kept open."""
+    token = _make_token()
+    with TestClient(app) as client, client.websocket_connect(f"/api/v1/status/ws/status?token={token}") as ws:
+        # Connection is open — we can send a ping and it should not raise
+        ws.send_text("ping")
+            # Server keeps the connection open (no disconnect expected)
+
+
+# ---------------------------------------------------------------------------
+# broadcast_status
+# ---------------------------------------------------------------------------
+
+@pytest.mark.asyncio
+async def test_broadcast_status_sends_to_connected_clients():
+    """broadcast_status sends a JSON message to all active connections."""
+    received: list[str] = []
+
+    class FakeWS:
+        async def send_text(self, text: str) -> None:
+            received.append(text)
+
+    fake = FakeWS()
+    _connections.append(fake)
+    try:
+        await broadcast_status(
+            node_id="node-1",
+            status="online",
+            checked_at="2024-01-01T00:00:00",
+            response_time_ms=42,
+        )
+    finally:
+        _connections.remove(fake)
+
+    assert len(received) == 1
+    msg = json.loads(received[0])
+    assert msg["type"] == "status"
+    assert msg["node_id"] == "node-1"
+    assert msg["status"] == "online"
+    assert msg["response_time_ms"] == 42
+
+
+@pytest.mark.asyncio
+async def test_broadcast_status_no_response_time():
+    """response_time_ms defaults to None."""
+    received: list[str] = []
+
+    class FakeWS:
+        async def send_text(self, text: str) -> None:
+            received.append(text)
+
+    fake = FakeWS()
+    _connections.append(fake)
+    try:
+        await broadcast_status(node_id="n", status="offline", checked_at="t")
+    finally:
+        _connections.remove(fake)
+
+    msg = json.loads(received[0])
+    assert msg["response_time_ms"] is None
+
+
+@pytest.mark.asyncio
+async def test_broadcast_status_removes_dead_connection():
+    """A connection that raises on send is removed from _connections."""
+
+    class DeadWS:
+        async def send_text(self, _: str) -> None:
+            raise RuntimeError("disconnected")
+
+    dead = DeadWS()
+    _connections.append(dead)
+    initial_len = len(_connections)
+
+    await broadcast_status(node_id="n", status="online", checked_at="t")
+
+    assert dead not in _connections
+    assert len(_connections) == initial_len - 1
+
+
+# ---------------------------------------------------------------------------
+# broadcast_scan_update
+# ---------------------------------------------------------------------------
+
+@pytest.mark.asyncio
+async def test_broadcast_scan_update():
+    """broadcast_scan_update sends scan_device_found payload."""
+    received: list[str] = []
+
+    class FakeWS:
+        async def send_text(self, text: str) -> None:
+            received.append(text)
+
+    fake = FakeWS()
+    _connections.append(fake)
+    try:
+        await broadcast_scan_update(run_id="run-42", devices_found=3)
+    finally:
+        _connections.remove(fake)
+
+    assert len(received) == 1
+    msg = json.loads(received[0])
+    assert msg["type"] == "scan_device_found"
+    assert msg["run_id"] == "run-42"
+    assert msg["devices_found"] == 3
+
+
+@pytest.mark.asyncio
+async def test_broadcast_no_connections():
+    """broadcast_* with no connections must not raise."""
+    assert len(_connections) == 0
+    await broadcast_status(node_id="n", status="online", checked_at="t")
+    await broadcast_scan_update(run_id="r", devices_found=0)