On the way to building a tree

tree.rb

class Tree
  def initialize
    @root = nil
  end

  def add_node(value)
  end

  def ensure_consistency(node)
    if node.nil?
      return true
    end

    if (node.left.value < node.value || node.right.value < node.value) ||
      (node.left_children_count - node.right_children_count).abs > 1
      return false
    else
      return ensure_consistency(node.left) && ensure_consistency(node.right)
    end
  end

  def remove_top_node
  end

  class Node
    attr_accessor :left, :right, :value, :left_children_count, :right_children_count

    def initialize(value)
      @left_children_count = 0
      @right_children_count = 0
      @value = value
      @left = nil
      @right = nil
    end
  end
end