[
  {
    "id": "$project example",
    "stage": "$project",
    "kind": "example",
    "pipeline": [
      {
        "$project": {
          "name": 1,
          "total": {
            "$multiply": [
              "$quantity",
              "$price"
            ]
          }
        }
      }
    ],
    "input": [
      {
        "_id": 7,
        "name": "Pen",
        "quantity": 2,
        "price": 5
      }
    ],
    "result": [
      {
        "name": "Pen",
        "total": 10.0
      }
    ]
  },
  {
    "id": "$project empty input",
    "stage": "$project",
    "kind": "empty input",
    "pipeline": [
      {
        "$project": {
          "name": 1,
          "total": {
            "$multiply": [
              "$quantity",
              "$price"
            ]
          }
        }
      }
    ],
    "input": [],
    "result": []
  },
  {
    "id": "$project invalid specification",
    "stage": "$project",
    "kind": "invalid specification",
    "pipeline": [
      {
        "$project": null
      }
    ],
    "input": [
      {
        "_id": 7,
        "name": "Pen",
        "quantity": 2,
        "price": 5
      }
    ],
    "error": "IllegalArgumentException",
    "message": "$project stage requires an object"
  },
  {
    "id": "$project exclusion only",
    "stage": "$project",
    "kind": "exclusion only",
    "pipeline": [
      {
        "$project": {
          "price": 0
        }
      }
    ],
    "input": [
      {
        "name": "Pen",
        "price": 5
      }
    ],
    "result": [
      {}
    ]
  },
  {
    "id": "$project missing field",
    "stage": "$project",
    "kind": "missing field",
    "pipeline": [
      {
        "$project": {
          "unknown": 1
        }
      }
    ],
    "input": [
      {}
    ],
    "result": [
      {
        "unknown": null
      }
    ]
  }
]