mutter/clutter/tests/conform/scripts/test-script-object-property.json

{
  "id" : "test",
  "type" : "ClutterActor",
  "layout-manager" : { "id" : "layout", "type" : "ClutterBoxLayout" },
  "children" : [
    {
      "id" : "child-1",
      "type" : "ClutterRectangle",
      "width" : "3 em",
      "height" : "3 em"
    }
  ]
}