shopify_api/test/fixtures/discount_code_batch_discount_codes.json

{
  "discount_codes": [
    {
      "id": null,
      "code": "SUMMER1",
      "errors": {}
    },
    {
      "id": null,
      "code": "SUMMER2",
      "errors": {}
    },
    {
      "id": null,
      "code": "SUMMER2",
      "errors": {
        "code": ["must be unique"]
      }
    }
  ]
}