{
  "_comment": [
    "Inputs only. Expectations are measured -- see record.js.",
    "`$currentDate`, the one update operator whose result cannot be recorded",
    "as a value: it is whatever the clock said. `volatile` names the fields",
    "whose recorded value is replaced by a `$$type` assertion, so the case",
    "still pins the type, the position and every other field of the document",
    "-- everything except the number nobody can predict."
  ],
  "documents": [{ "_id": 1, "a": 1 }],
  "cases": [
    {
      "description": "$currentDate with true writes a date",
      "volatile": ["d"],
      "operation": "updateOne",
      "arguments": { "filter": {}, "update": { "$currentDate": { "d": true } } }
    },
    {
      "description": "$currentDate with an explicit date type",
      "volatile": ["d"],
      "operation": "updateOne",
      "arguments": { "filter": {}, "update": { "$currentDate": { "d": { "$type": "date" } } } }
    },
    {
      "description": "$currentDate with the timestamp type",
      "volatile": ["d"],
      "operation": "updateOne",
      "arguments": { "filter": {}, "update": { "$currentDate": { "d": { "$type": "timestamp" } } } }
    },
    {
      "description": "$currentDate overwrites a field that is already there",
      "volatile": ["a"],
      "operation": "updateOne",
      "arguments": { "filter": {}, "update": { "$currentDate": { "a": true } } }
    },
    {
      "description": "$currentDate down a dotted path",
      "volatile": ["n.d"],
      "operation": "updateOne",
      "arguments": { "filter": {}, "update": { "$currentDate": { "n.d": true } } }
    },
    {
      "description": "$currentDate beside another operator",
      "volatile": ["d"],
      "operation": "updateOne",
      "arguments": { "filter": {}, "update": { "$currentDate": { "d": true }, "$inc": { "a": 1 } } }
    },
    {
      "description": "$currentDate with false, which is still a date",
      "volatile": ["d"],
      "operation": "updateOne",
      "arguments": { "filter": {}, "update": { "$currentDate": { "d": false } } }
    },
    {
      "description": "$currentDate with an unknown type name",
      "operation": "updateOne",
      "arguments": { "filter": {}, "update": { "$currentDate": { "d": { "$type": "nope" } } } }
    },
    {
      "description": "$currentDate with a document that is not $type",
      "operation": "updateOne",
      "arguments": { "filter": {}, "update": { "$currentDate": { "d": { "a": 1 } } } }
    },
    {
      "description": "$currentDate with a number",
      "operation": "updateOne",
      "arguments": { "filter": {}, "update": { "$currentDate": { "d": 1 } } }
    },
    {
      "description": "$currentDate on an upsert that inserts",
      "documents": [],
      "volatile": ["d"],
      "operation": "updateOne",
      "arguments": {
        "filter": { "k": 1 },
        "update": { "$currentDate": { "d": true } },
        "upsert": true
      }
    }
  ]
}