{
  "description": "Empty cache field in root level extension",
  "mockBidRequest": {
    "id": "some-request-id",
    "site": {
      "page": "test.somepage.com"
    },
    "imp": [
      {
        "id": "my-imp-id",
        "video": {
          "mimes": [
            "video/mp4"
            ]
        },
        "ext": {
          "appnexus": {
            "placementId": 12883451
          }
        }
      }
    ],
    "ext": {
      "prebid": {
        "cache": {}
      }
    }
  },
  "expectedReturnCode": 400,
  "expectedErrorMessage": "Invalid request: request.ext is invalid: request.ext.prebid.cache requires one of the \"bids\" or \"vastxml\" properties\n"
}