Practice by implementing bubble sort in Ruby

bubble_sort.rb

require 'byebug'
require 'rspec'

class BubbleSort
  attr_reader :arr
  def initialize(input)
    @arr = input
  end

  def bubble_bubble
    return if @arr.size <= 1
    loop do
      bubble_up
      return if @stop_flag
    end
  end

  def bubble_up
    @stop_flag = true
    @arr.each_with_index do |element, index|
      return if index == @arr.size - 1
      if element > @arr[index + 1]
        @stop_flag = false
        @arr.delete_at(index)
        @arr.insert(index + 1, element)
      end
    end
  end
end

RSpec.describe 'Bubble sort' do
  it 'sorts first pass' do
    a = [3, 2, 1]
    @b = BubbleSort.new(a)
    @b.bubble_up()
    expect(@b.instance_variable_get(:@stop_flag)).to eq(false)
    expect(@b.arr).to eq([2, 1, 3])
  end
  it 'sets continue to false when all sorted' do
    a = [1, 2, 3]
    @b = BubbleSort.new(a)
    @b.bubble_up()
    expect(@b.instance_variable_get(:@stop_flag)).to eq(true)
    expect(@b.arr).to eq([1, 2, 3])
  end
  it 'repeats the bubbling multiple times' do
    a = [3, 2, 1]
    @b = BubbleSort.new(a)
    @b.bubble_bubble()
    expect(@b.arr).to eq([1, 2, 3])
  end
  it 'works with about 10 digits' do
    a = [3, 6, 8, 1, 7, 2, 9, 5, 4]
    @b = BubbleSort.new(a)
    @b.bubble_bubble()
    expect(@b.arr).to eq([1, 2, 3, 4, 5, 6, 7, 8, 9])
  end
  it 'stops executing if array is equal to 1' do
    a = [7]
    @b = BubbleSort.new(a)
    expect(@b).to_not receive(:bubble_up)
    @b.bubble_bubble()
  end
  it 'wont execute a 0 length array' do
    a = []
    @b = BubbleSort.new(a)
    expect(@b).to_not receive(:bubble_up)
    @b.bubble_bubble()
  end
end