{
  "synthetic": true,
  "scope": "Finite offline teaching model, not production implementation.",
  "function": "dateOnly",
  "cases": [
    {
      "id": 1,
      "args": [
        "2026-10-18"
      ],
      "expected": "2026-10-18"
    },
    {
      "id": 2,
      "args": [
        "2026-02-30"
      ],
      "expected": null
    },
    {
      "id": 3,
      "args": [
        "18/10/2026"
      ],
      "expected": null
    }
  ]
}