v1.9.4/command/test-fixtures/validate/null_var.json

{
    "variables": {
        "null_var": null
    },
    "builders": [{
        "type": "null",
        "communicator": "none"
    }],
    "provisioners": [
        {
            "type": "shell-local",
            "inline": "echo yop"
        }
    ]
}