feat(_shared): 워커 heartbeat 모듈 (worker:<name>:heartbeat TTL SET)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

services/_shared/tests/test_heartbeat.py

@@ -0,0 +1,46 @@
+"""Tests for _shared.heartbeat — Task A1."""
+import json
+import sys
+from pathlib import Path
+
+import pytest
+
+# Make `_shared` importable (same pattern as test_reliable_queue.py)
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent.parent))
+
+from _shared.heartbeat import WorkerStats, build_payload, render_state
+
+
+def test_build_payload_has_contract_fields():
+    s = WorkerStats(); s.jobs_done = 3; s.last_job_at = "2026-06-29T00:00:00Z"
+    payload = json.loads(build_payload("image-render", "render", "idle", s))
+    assert payload["name"] == "image-render"
+    assert payload["kind"] == "render"
+    assert payload["state"] == "idle"
+    assert payload["jobs_done"] == 3
+    assert payload["last_job_at"] == "2026-06-29T00:00:00Z"
+    assert payload["ts"].endswith("Z")
+
+
+def test_build_payload_merges_extra():
+    payload = json.loads(build_payload("task-watcher", "watcher", "free", WorkerStats(), extra={"mode": "free"}))
+    assert payload["mode"] == "free"
+
+
+class _FakeRedis:
+    def __init__(self, paused): self._paused = paused
+    async def get(self, key): return b"1" if self._paused else None
+
+
+@pytest.mark.asyncio
+async def test_render_state_paused_overrides_busy():
+    s = WorkerStats(); s.busy = True
+    assert await render_state(_FakeRedis(paused=True), s) == "paused"
+
+
+@pytest.mark.asyncio
+async def test_render_state_busy_then_idle():
+    s = WorkerStats(); s.busy = True
+    assert await render_state(_FakeRedis(paused=False), s) == "busy"
+    s.busy = False
+    assert await render_state(_FakeRedis(paused=False), s) == "idle"