PHPUnit_Util_XML::cssSelect PHP Method

    public static function cssSelect($selector, $content, $actual, $isHtml = TRUE)
    {
        $matcher = self::convertSelectToTag($selector, $content);
        $dom = self::load($actual, $isHtml);
        $tags = self::findNodes($dom, $matcher, $isHtml);
        return $tags;
    }

 /**
  * Assert function to determine if tips rendered to the page
  * have a corresponding page element.
  *
  * @param array $tips
  *   A list of tips which provide either a "data-id" or "data-class".
  *
  * @code
  * // Basic example.
  * $this->assertTourTips();
  *
  * // Advanced example. The following would be used for multipage or
  * // targeting a specific subset of tips.
  * $tips = array();
  * $tips[] = array('data-id' => 'foo');
  * $tips[] = array('data-id' => 'bar');
  * $tips[] = array('data-class' => 'baz');
  * $this->assertTourTips($tips);
  * @endcode
  */
 public function assertTourTips($tips = array())
 {
     // Get the rendered tips and their data-id and data-class attributes.
     if (empty($tips)) {
         // Tips are rendered as <li> elements inside <ol id="tour">.
         $rendered_tips = $this->xpath('//ol[@id = "tour"]//li[starts-with(@class, "tip")]');
         foreach ($rendered_tips as $rendered_tip) {
             $attributes = (array) $rendered_tip->attributes();
             $tips[] = $attributes['@attributes'];
         }
     }
     // If the tips are still empty we need to fail.
     if (empty($tips)) {
         $this->fail('Could not find tour tips on the current page.');
     } else {
         // Check for corresponding page elements.
         $total = 0;
         $modals = 0;
         foreach ($tips as $tip) {
             if (!empty($tip['data-id'])) {
                 $elements = \PHPUnit_Util_XML::cssSelect('#' . $tip['data-id'], TRUE, $this->content, TRUE);
                 $this->assertTrue(!empty($elements) && count($elements) === 1, format_string('Found corresponding page element for tour tip with id #%data-id', array('%data-id' => $tip['data-id'])));
             } elseif (!empty($tip['data-class'])) {
                 $elements = \PHPUnit_Util_XML::cssSelect('.' . $tip['data-class'], TRUE, $this->content, TRUE);
                 $this->assertFalse(empty($elements), format_string('Found corresponding page element for tour tip with class .%data-class', array('%data-class' => $tip['data-class'])));
             } else {
                 // It's a modal.
                 $modals++;
             }
             $total++;
         }
         $this->pass(format_string('Total %total Tips tested of which %modals modal(s).', array('%total' => $total, '%modals' => $modals)));
     }
 }