{
  "description": "Required appnexus bidder param is provided but the type is invalid",
  "config": {
    "realParamsValidator": true
  },
  "mockBidRequest": {
    "id": "some-request-id",
    "site": {
      "page": "prebid.org"
    },
    "imp": [
      {
        "id": "some-impression-id",
        "banner": {
          "format": [
            {
              "w": 300,
              "h": 250
            },
            {
              "w": 300,
              "h": 600
            }
          ]
        },
        "ext": {
          "appnexus": {
            "placementId": []
          }
        }
      }
    ],
    "tmax": 500,
    "ext": {}
  },
  "expectedReturnCode": 400,
  "expectedErrorMessage": "Invalid request: request.imp[0].ext.prebid.bidder.appnexus failed validation.\nplacementId: Invalid type. Expected: [integer,string], given: array\n"
}