{
  "tests": [
    {
      "description": "update: last-update-time precondition",
      "comment": "The Update call supports a last-update-time precondition.",
      "update": {
        "docRefPath": "projects/projectID/databases/(default)/documents/C/d",
        "precondition": {
          "updateTime": "1970-01-01T00:00:42Z"
        },
        "jsonData": "{\"a\": 1}",
        "request": {
          "database": "projects/projectID/databases/(default)",
          "writes": [
            {
              "update": {
                "name": "projects/projectID/databases/(default)/documents/C/d",
                "fields": {
                  "a": {
                    "integerValue": "1"
                  }
                }
              },
              "updateMask": {
                "fieldPaths": [
                  "a"
                ]
              },
              "currentDocument": {
                "updateTime": "1970-01-01T00:00:42Z"
              }
            }
          ]
        }
      }
    }
  ]
}