{
  "description": "Bid request's sole imp element has empty extension",
  "mockBidRequest": {
    "id": "req-id",
    "imp": [
      {
        "id": "imp-id",
        "video": {
          "mimes": [
            "video/mp4"
            ]
        },
        "ext": {}
      }
    ],
    "app": {
      "id": "app_001"
    }
  },
  "expectedReturnCode": 400,
  "expectedErrorMessage": "Invalid request: request.imp[0].ext.prebid.bidder must contain at least one bidder\n"
}