Merkle tree in ruby

merkle.rb

#!/usr/bin/env ruby

class Merkle
  attr_accessor :key, :parent, :left, :right
  def initialize(array, parent = nil)
    @parent = parent
    @key = array.join
    load(array)
  end

  def load(array)
    return if (array.length < 2)
    mid = (array.length / 2).floor
    if (mid != 1 && mid % 2 != 0)
      mid += 1
    end
    @left = Merkle.new(array[0..(mid - 1)], self)
    @right = Merkle.new(array[mid..-1], self)
  end
end

require 'minitest/autorun'
describe Merkle do
  describe "#new" do
    describe "works with 2" do
      before do
        @m = Merkle.new(['a', 'b'])
      end
      it "should have 2 nodes" do
        @m.key.must_equal("ab")
        @m.left.key.must_equal("a")
        @m.right.key.must_equal("b")
        @m.right.parent.key.must_equal("ab")
      end
    end
    describe "works with 6" do
      before do
        @m = Merkle.new(['a', 'b', 'c', 'd', 'e', 'f'])
      end
      it "should have 6 nodes" do
        @m.key.must_equal("abcdef")
        @m.left.key.must_equal("abcd")
        @m.left.left.key.must_equal("ab")
        @m.left.left.left.key.must_equal("a")
        @m.right.key.must_equal("ef")
        @m.right.right.key.must_equal("f")
      end
    end
    describe "works with 11" do
      before do
        @m = Merkle.new(['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k'])
      end
      it "should have 11 nodes" do
        @m.key.must_equal("abcdefghijk")

        @m.left.key.must_equal("abcdef")
        @m.left.left.key.must_equal("abcd")
        @m.left.left.left.key.must_equal("ab")
        @m.left.left.left.left.key.must_equal("a")

        @m.right.key.must_equal("ghijk")
        @m.right.right.key.must_equal("ijk")
        @m.right.right.right.key.must_equal("jk")
        @m.right.right.right.right.key.must_equal("k")
      end
    end
    describe "works with 12" do
      before do
        @m = Merkle.new(['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l'])
      end
      it "should have 12 nodes" do
        @m.key.must_equal("abcdefghijkl")
        @m.left.key.must_equal("abcdef")
        @m.left.left.key.must_equal("abcd")
        @m.left.left.left.key.must_equal("ab")
        @m.left.left.left.left.key.must_equal("a")
        @m.right.key.must_equal("ghijkl")
        @m.right.right.key.must_equal("kl")
        @m.right.right.right.key.must_equal("l")
      end
    end
  end
end