{
  "expression": ["let", "a", ["get", "x"], ["+", 1, ["number", ["var", "a"]]]],
  "inputs": [[{}, {"properties": {"x": 5}}]],
  "expected": {
    "compiled": {
      "result": "success",
      "isFeatureConstant": false,
      "isZoomConstant": true,
      "type": "number"
    },
    "outputs": [6],
    "serialized": ["let", "a", ["get", "x"], ["+", 1, ["number", ["var", "a"]]]]
  }
}