anchor.diff:            elevation = 0;
           };
           frontend = {};
  -        # uses embedded mqtt broker
  -        mqtt.password = mqttPassword;
  +        mqtt = {
  +          broker = "127.0.0.1";
  +          username = mqttUsername;
  +          password = mqttPassword;
  +        };
           binary_sensor = [{
             platform = "mqtt";
             state_topic = "home-assistant/test";
  
positive.code: 
  let
    configDir = "/var/lib/foobar";
    mqttPassword = "secret";
  in {
    name = "home-assistant";
  
negative.code: 
    nodes.hass = { pkgs, ... }: {
      environment.systemPackages = with pkgs; [ mosquitto ];
      services.mosquitto = {
        enable = true;
        users = {
          "${mqttUsername}" = {
            acl = [ "pattern readwrite #" ];
            password = mqttPassword;
          };
        };
      };
      services.home-assistant = {
        inherit configDir;
        enable = true;
  