Ruby method to keep track of files written to while executing given block

written_files_tracking.rb

class WrittenFilesTracking
  def self.written_files
    @@written_files
  end

  def self.start_with
    @@start_with
  end

  def self.with(start_with:'./')
    @@start_with = start_with
    @@written_files = []
    begin
      class << File
        alias_method :__written_files_open, :open
        def __written_files_tracing_open(*args, &block)
          if args[0].start_with?(WrittenFilesTracking.start_with) && args[1] =~ /w/
            WrittenFilesTracking.written_files.push(args[0])
          end
          __written_files_open(*args, &block)
        end
        alias_method :open, :__written_files_tracing_open
      end
      yield
    ensure
      class << File
        alias_method :open, :__written_files_open
        remove_method :__written_files_open
        remove_method :__written_files_tracing_open
      end
    end
  end
end