Round 3 fixes: cancelled polling, aggregator invalid_count, filter state, scheduler atomicity, HTTP exception handler, tests

tests/integration/test_proxies_api.py

@@ -137,6 +137,15 @@ class TestProxiesAPI:
         assert response.status_code == 200
         assert response.headers["content-type"] == "application/json"
 
+    @pytest.mark.asyncio
+    async def test_export_proxies_json_empty_database(self, client):
+        """测试 GET /api/proxies/export/json - 空数据库"""
+        response = await client.get("/api/proxies/export/json")
+        assert response.status_code == 200
+        assert response.headers["content-type"] == "application/json"
+        # 空数据库应返回空列表 JSON
+        assert response.content.strip() == b"[]"
+
     @pytest.mark.asyncio
     async def test_export_proxies_invalid_format(self, client):
         """测试 GET /api/proxies/export/invalid - 无效格式"""