grouper and unit test

grouper.rb

class Grouper

  def self.group(list)
    result = list.inject([]) do |res, gr1|
      current_group = recursive_finder(list, gr1)
      res << current_group
    end
    result | list
  end

  def self.recursive_finder(list, group)
    current_group = group
    list.each do |gr2|
      if similar? current_group, gr2
        list.delete group
        list.delete gr2
        current_group |= gr2 | recursive_finder(list, gr2)
      end
    end
    current_group
  end

  def self.similar?(list1, list2)
    for el in list1
      return true if list2.include?(el)
    end
    false
  end

end

grouper_spec.rb

require_relative "../lib/grouper"
describe Grouper do

  before(:each) do
    @list = [[1,2],[2,6],[3],[4,5],[5,1]]
  end

  it "should return true if two arrays have similar element" do
    list1 = [1,2,3]
    list2 = [3,4,5]
    Grouper.similar?(list1, list2).should be true
  end

  it "should return false if there are no common element" do
    list1 = [1,2,3]
    list2 = [4,5,5]
    Grouper.similar?(list1, list2).should be false
  end

  it "should return the list of groups" do
    Grouper.group(@list).should == [[1,2,6,5,4],[3]]
  end

  it "should return identical array when there are no common elements" do
    list2 = [[1,2],[3,4],[5,6]]
    Grouper.group(list2).should == [[1,2],[5,6],[3,4]]
  end

  it "should return exact 1 array in array when all elements are common" do
    list2 = [[1,2],[2,1]]
    Grouper.group(list2).should == [[1,2]]
  end

end