{
  "fixture": "OPC UA 轮询变化记录",
  "cases": [
    {
      "case_id": "重复轮询值与状态变化",
      "kind": "正例",
      "result": {
        "reads": [
          {
            "value": 25,
            "status": 0,
            "source": "2026-10-24T10:00:00Z",
            "server": "2026-10-24T10:00:00Z"
          },
          {
            "value": 25,
            "status": 0,
            "source": "2026-10-24T10:00:00Z",
            "server": "2026-10-24T10:00:10Z"
          },
          {
            "value": 26,
            "status": 0,
            "source": "2026-10-24T10:00:12Z",
            "server": "2026-10-24T10:00:20Z"
          },
          {
            "value": 26,
            "status": 1073741824,
            "source": "2026-10-24T10:00:22Z",
            "server": "2026-10-24T10:00:30Z"
          },
          {
            "value": 27,
            "status": 0,
            "source": null,
            "server": "2026-10-24T10:00:40Z"
          }
        ],
        "source_changes": [
          {
            "read": 0,
            "value": 25,
            "status": 0,
            "source_time": "2026-10-24T10:00:00Z",
            "evidence": "initial_observation"
          },
          {
            "read": 2,
            "value": 26,
            "status": 0,
            "source_time": "2026-10-24T10:00:12Z",
            "evidence": "value_changed"
          },
          {
            "read": 3,
            "value": 26,
            "status": 1073741824,
            "source_time": "2026-10-24T10:00:22Z",
            "evidence": "status_changed"
          },
          {
            "read": 4,
            "value": 27,
            "status": 0,
            "source_time": null,
            "evidence": "source_time_unknown"
          }
        ],
        "read_count": 5,
        "observed_change_count": 3
      }
    },
    {
      "case_id": "变化却复用源时间矛盾",
      "kind": "正例",
      "result": {
        "reads": [
          {
            "value": 1,
            "status": 0,
            "source": "2026-10-24T10:00:00Z",
            "server": "2026-10-24T10:00:00Z"
          },
          {
            "value": 2,
            "status": 0,
            "source": "2026-10-24T10:00:00Z",
            "server": "2026-10-24T10:00:10Z"
          }
        ],
        "source_changes": [
          {
            "read": 0,
            "value": 1,
            "status": 0,
            "source_time": "2026-10-24T10:00:00Z",
            "evidence": "initial_observation"
          },
          {
            "read": 1,
            "value": 2,
            "status": 0,
            "source_time": null,
            "evidence": "contradictory_source_time"
          }
        ],
        "read_count": 2,
        "observed_change_count": 1
      }
    },
    {
      "case_id": "缺少质量字段",
      "kind": "显式负例",
      "rejected": "原始证据缺必要字段"
    }
  ],
  "assertions_passed": 3,
  "scope": "合成输入离线演算；未接真实设备"
}