raise Error, "Can not find Firefox browser binary #{settings[:firefox_binary_path]}." if settings[:browser] == :firefox && !settings[:firefox_binary_path].blank? && !File.exist?(settings[:firefox_binary_path])
    raise Error, "Can not find chromedriver #{ settings[:chromedriver_path] }." if settings[:browser] == :chrome && !settings[:chromedriver_path].blank? && !File.exist?(settings[:chromedriver_path])