[
  {
    "id": "$replaceWith example",
    "stage": "$replaceWith",
    "kind": "example",
    "pipeline": [
      {
        "$replaceWith": "$address"
      }
    ],
    "input": [
      {
        "name": "Alice",
        "address": {
          "city": "Toronto"
        }
      }
    ],
    "result": [
      {
        "city": "Toronto"
      }
    ]
  },
  {
    "id": "$replaceWith empty input",
    "stage": "$replaceWith",
    "kind": "empty input",
    "pipeline": [
      {
        "$replaceWith": "$address"
      }
    ],
    "input": [],
    "result": []
  },
  {
    "id": "$replaceWith invalid specification",
    "stage": "$replaceWith",
    "kind": "invalid specification",
    "pipeline": [
      {
        "$replaceWith": null
      }
    ],
    "input": [
      {
        "name": "Alice",
        "address": {
          "city": "Toronto"
        }
      }
    ],
    "error": "IllegalArgumentException",
    "message": "$replaceWith stage requires an expression"
  },
  {
    "id": "$replaceWith missing root",
    "stage": "$replaceWith",
    "kind": "missing root",
    "pipeline": [
      {
        "$replaceWith": "$address"
      }
    ],
    "input": [
      {}
    ],
    "error": "IllegalArgumentException",
    "message": "$replaceRoot evaluated to non-object: null"
  }
]