'Tannenbaum' in groovy. Tests?

gistfile1.groovy

def tree(height, with_star = true) {
  if (with_star) println(" " * (left_padding(height, 0) - 1) + "*")
  (1..height).each {
    ring(it, height)
  }
  println(" " * (left_padding(height, 0) - 1) + "X")
}

def ring(from_top, height) {
  println(" " * left_padding(height, from_top) + "X" * (2 * from_top - 1))
}

def left_padding(height, from_top) {
  height - from_top
}

tree(15)