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backend/tests/test_cache_local.py

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+"""cache.py 本地层（不碰 Redis）：TTL 过期、容量淘汰、熔断冷却恢复。"""
+from __future__ import annotations
+
+import pytest
+
+import app.cache as cache_mod
+from app import cache
+
+
+class _FakeClock:
+    """替换 cache 命名空间里的 time（不影响全局 time 模块）。"""
+
+    def __init__(self):
+        self.now = 1000.0
+
+    def monotonic(self) -> float:
+        return self.now
+
+    def time(self) -> float:
+        return self.now
+
+
+@pytest.fixture(autouse=True)
+def _reset_state():
+    """每个用例干净的本地缓存状态。"""
+    cache._local_store.clear()
+    cache._local_bytes = 0
+    cache._disabled_until = 0.0
+    yield
+    cache._local_store.clear()
+    cache._local_bytes = 0
+    cache._disabled_until = 0.0
+
+
+def test_local_set_get_roundtrip():
+    cache.local_set("k", '{"a":1}', ttl=60)
+    assert cache.local_get("k") == '{"a":1}'
+
+
+def test_local_get_miss():
+    assert cache.local_get("nope") is None
+
+
+def test_local_expiry(monkeypatch):
+    clock = _FakeClock()
+    monkeypatch.setattr(cache_mod, "time", clock)
+    cache.local_set("k", "v", ttl=10)
+    clock.now = 1005.0
+    assert cache.local_get("k") == "v"
+    clock.now = 1101.0  # 过期
+    assert cache.local_get("k") is None
+    assert "k" not in cache._local_store  # 过期读取顺手清理
+
+
+def test_local_ttl_capped_at_120s():
+    """本地层恒 ≤120s（多进程部署时最多比 Redis 多陈旧 120s 的约定）。"""
+    base = cache.time.monotonic()
+    cache.local_set("k", "v", ttl=99999)
+    ent = cache._local_store["k"]
+    assert ent[0] - base <= 120.0 + 5  # 相对当前 monotonic 的上限（留误差余量）
+
+
+def test_local_entries_cap_evicts_oldest():
+    for i in range(cache._LOCAL_MAX_ENTRIES + 5):
+        cache.local_set(f"k{i}", "v", ttl=60)
+    assert len(cache._local_store) <= cache._LOCAL_MAX_ENTRIES
+    # 先插入的（最旧）被近似 LRU 淘汰
+    assert cache.local_get("k0") is None
+    assert cache.local_get(f"k{cache._LOCAL_MAX_ENTRIES + 4}") == "v"
+
+
+def test_local_overwrite_releases_bytes():
+    cache.local_set("k", "x" * 1000, ttl=60)
+    before = cache._local_bytes
+    cache.local_set("k", "y", ttl=60)
+    assert cache._local_bytes < before
+    assert cache.local_get("k") == "y"
+
+
+def test_bail_cooldown_recovers(monkeypatch):
+    """熔断 60s：期间 _client 为 None，到期自动放行（Redis 未配置时也返回 None，但不熔断）。"""
+    clock = _FakeClock()
+    monkeypatch.setattr(cache_mod, "time", clock)
+    cache._bail()
+    assert cache._disabled_until > clock.now
+    clock.now += 59.0
+    assert clock.monotonic() < cache._disabled_until  # 仍在熔断期
+    clock.now += 2.0  # 越过 60s 冷却
+    assert clock.monotonic() >= cache._disabled_until  # 恢复探测资格
+
+
+def test_digest_stable_and_distinct():
+    assert cache.digest("a", 1, None) == cache.digest("a", 1, None)
+    assert cache.digest("a", 1) != cache.digest("a", 2)