def cpp_files_in(some_dir)
      raise ArgumentError, 'some_dir is not a Pathname' unless some_dir.is_a? Pathname
      return [] unless some_dir.exist? && some_dir.directory?

      real = some_dir.realpath
      files = Find.find(real).map { |p| Pathname.new(p) }.reject(&:directory?)
      cpp = files.select { |path| CPP_EXTENSIONS.include?(path.extname.downcase) }
      not_hidden = cpp.reject { |path| path.basename.to_s.start_with?(".") }
      not_hidden.sort_by(&:to_s)
    end
def cpp_files_in(some_dir)
      raise ArgumentError, 'some_dir is not a Pathname' unless some_dir.is_a? Pathname
      return [] unless some_dir.exist? && some_dir.directory?

      real = some_dir.realpath
      files = Find.find(real).map { |p| Pathname.new(p) }.reject(&:directory?)
      cpp = files.select { |path| CPP_EXTENSIONS.include?(path.extname.downcase) }
      not_hidden = cpp.reject { |path| path.basename.to_s.start_with?(".") }
      not_hidden.sort_by(&:to_s)
    end
Get a list of all CPP source files in a directory and its subdirectories
 @param some_dir [Pathname] The directory in which to begin the search
 @return [Array<Pathname>] The paths of the found files