assert_select (ActionController::Assertions::SelectorAssertions)

    # File lib/action_controller/assertions/selector_assertions.rb, line 193
          def assert_select(*args, &block)
            # Start with optional element followed by mandatory selector.
            arg = args.shift

            if arg.is_a?(HTML::Node)
              # First argument is a node (tag or text, but also HTML root),
              # so we know what we're selecting from.
              root = arg
              arg = args.shift
            elsif arg == nil
              # This usually happens when passing a node/element that
              # happens to be nil.
              raise ArgumentError, "First argument is either selector or element to select, but nil found. Perhaps you called assert_select with an element that does not exist?"
            elsif @selected
              root = HTML::Node.new(nil)
              root.children.concat @selected
            else
              # Otherwise just operate on the response document.
              root = response_from_page_or_rjs
            end

            # First or second argument is the selector: string and we pass
            # all remaining arguments. Array and we pass the argument. Also
            # accepts selector itself.
            case arg
              when String
                selector = HTML::Selector.new(arg, args)
              when Array
                selector = HTML::Selector.new(*arg)
              when HTML::Selector
                selector = arg
              else raise ArgumentError, "Expecting a selector as the first argument"
            end

            # Next argument is used for equality tests.
            equals = {}
            case arg = args.shift
              when Hash
                equals = arg
              when String, Regexp
                equals[:text] = arg
              when Integer
                equals[:count] = arg
              when Range
                equals[:minimum] = arg.begin
                equals[:maximum] = arg.end
              when FalseClass
                equals[:count] = 0
              when NilClass, TrueClass
                equals[:minimum] = 1
              else raise ArgumentError, "I don't understand what you're trying to match"
            end

            # By default we're looking for at least one match.
            if equals[:count]
              equals[:minimum] = equals[:maximum] = equals[:count]
            else
              equals[:minimum] = 1 unless equals[:minimum]
            end

            # Last argument is the message we use if the assertion fails.
            message = args.shift
            #- message = "No match made with selector #{selector.inspect}" unless message
            if args.shift
              raise ArgumentError, "Not expecting that last argument, you either have too many arguments, or they're the wrong type"
            end

            matches = selector.select(root)
            # If text/html, narrow down to those elements that match it.
            content_mismatch = nil
            if match_with = equals[:text]
              matches.delete_if do |match|
                text = ""
                text.force_encoding(match_with.encoding) if text.respond_to?(:force_encoding)
                stack = match.children.reverse
                while node = stack.pop
                  if node.tag?
                    stack.concat node.children.reverse
                  else
                    content = node.content
                    content.force_encoding(match_with.encoding) if content.respond_to?(:force_encoding)
                    text << content
                  end
                end
                text.strip! unless NO_STRIP.include?(match.name)
                unless match_with.is_a?(Regexp) ? (text =~ match_with) : (text == match_with.to_s)
                  content_mismatch ||= build_message(message, "<?> expected but was\n<?>.", match_with, text)
                  true
                end
              end
            elsif match_with = equals[:html]
              matches.delete_if do |match|
                html = match.children.map(&:to_s).join
                html.strip! unless NO_STRIP.include?(match.name)
                unless match_with.is_a?(Regexp) ? (html =~ match_with) : (html == match_with.to_s)
                  content_mismatch ||= build_message(message, "<?> expected but was\n<?>.", match_with, html)
                  true
                end
              end
            end
            # Expecting foo found bar element only if found zero, not if
            # found one but expecting two.
            message ||= content_mismatch if matches.empty?
            # Test minimum/maximum occurrence.
            min, max = equals[:minimum], equals[:maximum]
            message = message || %(Expected #{count_description(min, max)} matching "#{selector.to_s}", found #{matches.size}.)
            assert matches.size >= min, message if min
            assert matches.size <= max, message if max

            # If a block is given call that block. Set @selected to allow
            # nested assert_select, which can be nested several levels deep.
            if block_given? && !matches.empty?
              begin
                in_scope, @selected = @selected, matches
                yield matches
              ensure
                @selected = in_scope
              end
            end

            # Returns all matches elements.
            matches
          end