{
  "fixture": "Modbus Mask Write Register",
  "cases": [
    {
      "case_id": "保留高位改低位",
      "kind": "正例",
      "result": {
        "result": 4661,
        "preserved_mask": 65520,
        "controlled_mask": 15
      }
    },
    {
      "case_id": "OR不能覆盖被保留位",
      "kind": "正例",
      "result": {
        "result": 0,
        "preserved_mask": 65535,
        "controlled_mask": 0
      }
    },
    {
      "case_id": "全清",
      "kind": "正例",
      "result": {
        "result": 0,
        "preserved_mask": 0,
        "controlled_mask": 65535
      }
    },
    {
      "case_id": "超16位",
      "kind": "显式负例",
      "rejected": "字段超出16位"
    }
  ],
  "assertions_passed": 4,
  "scope": "合成输入离线演算；未接真实设备"
}