Arduino formatter for rspec

.rspec

--color
--require spec_helper
--format Fuubar
--format ArduinoFormatter

arduino_formatter.rb

class ArduinoFormatter
  # This registers the notifications this formatter supports, and tells
  # us that this was written against the RSpec 3.x formatter API.
  RSpec::Core::Formatters.register self, :start, :dump_failures

  def initialize(*args)
    system 'stty -F /dev/ttyACM0 9600 cs8'
    @tty = File.open('/dev/ttyACM0', 'w')
    # sleep(2) # if auto-reset is turned ON on the Arduino is on
  end

  def start(_)
    @tty.putc('y')
  end

  def dump_failures(notification)
    if notification.failure_notifications.empty?
      @tty.putc('g')
    else
      @tty.putc('r')
    end
    @tty.close
  end
end

sketch.ino

#define RED 10
#define YELLOW 11
#define GREEN 12

int incomingByte = 0;
int leds[3] = { RED, YELLOW, GREEN };
int leds_count = 3;

void setup() {
  for(int i = 0; i < 3; i++) {
    pinMode(leds[i], OUTPUT);
  }

  Serial.begin(9600);
}

void loop() {
}

void serialEvent() {
  incomingByte = Serial.read();

  switch(incomingByte) {
    case 103: // g, green
      turnOn(GREEN);
      break;
    case 121: // y, yellow
      turnOn(YELLOW);
      break;
    case 114: // r, red
      turnOn(RED);
      break;
  }
}

void turnOn(int pin) {
  for(int i = 0; i < 3; i++) {
    digitalWrite(leds[i], pin == leds[i]);
  }
}