Gets.chomp stubbing with Dependency Injection

di_example.rb

class InputFetcher
  def fetch
    gets.chomp
  end
end

class Game
  attr_reader :fetcher

  def initialize(fetcher_type = InputFetcher)
    @fetcher = fetcher_type.new
  end

  def play
    unless fetcher.fetch == "quit"
      puts "Still Going"
    end
    
    return "done"
  end
end

class GameTest < Minitest::Test
  class FakeFetcher
    def fetch
      "quit"
    end
  end
  
  def test_it_exits
    game = Game.new(FakeFetcher)
    assert_equal "done", game.play
  end
end