Tests preview provided by Runtime.getProperties.
p1 : Object
p2 : Object
p1 : {
    "type": "object",
    "description": "Object",
    "overflow": false,
    "properties": [
        {
            "name": "a",
            "type": "number",
            "value": "1"
        }
    ]
}
p2 : {
    "type": "object",
    "description": "Object",
    "overflow": false,
    "properties": [
        {
            "name": "b",
            "type": "string",
            "value": "foo"
        },
        {
            "name": "bb",
            "type": "string",
            "value": "bar"
        }
    ]
}