{
  "fixtures": [
    {
      "match": { "userMessage": "change background to blue" },
      "response": {
        "toolCalls": [{ "name": "change_background", "arguments": { "background": "blue" } }]
      }
    },
    {
      "match": { "toolCallId": "call_background" },
      "response": { "content": "Done! I've changed the background." }
    }
  ]
}