require 'test/unit'

class MyHash
  def initialize
    @array = []
  end

  def []=(key, value)
    object = @array.find do |key_value_pair|
      key_value_pair.first == key
    end

    if object
      object[1] = value
    else
      @array.push([key, value])
    end

    value
  end

  def [](key)
    object = find_object(key)

    if object
      object.last
    else
      nil
    end
  end

  private

  def find_object(key)
    @array.find do |pair|
      pair.first == key
    end
  end
end



class TestMyHash < Test::Unit::TestCase
  def setup
    @hash = MyHash.new
    @hash.instance_variable_set(:@array, [['k_1', 'v_1'], ['k_2', 'v_2']])
  end

  def test_set_update_internal_array
    @hash['k_3'] = 'v_3'
    assert_equal( @hash.instance_variable_get(:@array), [['k_1', 'v_1'], ["k_2", 'v_2'], ["k_3", 'v_3']])
  end

  def test_set_return_correct_value
    assert_equal( @hash['k_3'] = 'v_3', 'v_3')
  end

  def test_get_return_correct_value
    assert_equal( @hash['k_1'], 'v_1')
    assert_equal( @hash['k_2'], 'v_2')
  end

  def test_get_of_null_key
    assert_nil( @hash['non_exist_key'] )
  end

  def test_set_respecify_value
    assert_equal( @hash['k_1'], 'v_1')
    @hash['k_1'] = 'v_2'
    assert_equal( @hash['k_1'], 'v_2')
  end
end