firestore/internal/conformance/testdata/update-no-paths.json

{
  "tests": [
    {
      "description": "update: no paths",
      "comment": "It is a client-side error to call Update with empty data.",
      "update": {
        "docRefPath": "projects/projectID/databases/(default)/documents/C/d",
        "jsonData": "{}",
        "isError": true
      }
    }
  ]
}