{
  "fixture": "Modbus 异常 PDU 解析",
  "cases": [
    {
      "case_id": "异常地址",
      "kind": "正例",
      "result": {
        "kind": "exception",
        "request_fc": 3,
        "exception_code": 2,
        "name": "Illegal Data Address"
      }
    },
    {
      "case_id": "正常读数",
      "kind": "正例",
      "result": {
        "kind": "normal",
        "values": [
          42
        ]
      }
    },
    {
      "case_id": "未知异常码保留",
      "kind": "正例",
      "result": {
        "kind": "exception",
        "request_fc": 3,
        "exception_code": 127,
        "name": "未知异常码"
      }
    },
    {
      "case_id": "异常多字节",
      "kind": "显式负例",
      "rejected": "异常PDU应为两字节"
    },
    {
      "case_id": "请求功能不符",
      "kind": "显式负例",
      "rejected": "原始功能码不匹配"
    }
  ],
  "assertions_passed": 5,
  "scope": "合成输入离线演算；未接真实设备"
}