Groovy’s JsonBuilder makes it easy to create Json. For example to create this Json string:

String carRecords = '''
    {
        "records": {
        "car": {
            "name": "HSV Maloo",
            "make": "Holden",
            "year": 2006,
            "country": "Australia",
            "record": {
              "type": "speed",
              "description": "production pickup truck with speed of 271kph"
            }
          }
      }
    }
'''

you can use a JsonBuilder like this:

JsonBuilder builder = new JsonBuilder()
builder.records {
  car {
        name 'HSV Maloo'
        make 'Holden'
        year 2006
        country 'Australia'
        record {
            type 'speed'
            description 'production pickup truck with speed of 271kph'
        }
  }
}
String json = JsonOutput.prettyPrint(builder.toString())

We use JsonUnit to check that the builder produced the expected result:

JsonAssert.assertJsonEquals(json, carRecords)