# File lib/autotest.rb, line 306
  def find_files_to_test(files=find_files)
    updated = files.select { |filename, mtime|
      @files[filename] < mtime
    }

    p updated if $v unless updated.empty? or @last_mtime.to_i == 0

    # TODO: keep an mtime at app level and drop the files hash
    updated.each do |filename, mtime|
      @files[filename] = mtime
    end

    updated.each do |filename, mtime|
      tests_for_file(filename).each do |f|
        @files_to_test[f] # creates key with default value
      end
    end

    previous = @last_mtime
    @last_mtime = @files.values.max
    @last_mtime > previous
  end