fails:CGI::HtmlExtension#image_button when passed no arguments returns an image-'input'-element without a source image
fails:CGI::HtmlExtension#image_button when passed no arguments ignores a passed block
fails:CGI::HtmlExtension#image_button when passed src returns an image-'input'-element with the passed src
fails:CGI::HtmlExtension#image_button when passed src ignores a passed block
fails:CGI::HtmlExtension#image_button when passed src, name returns an image-'input'-element with the passed src and name
fails:CGI::HtmlExtension#image_button when passed src, name ignores a passed block
