];
$output = $renderer->renderRoot($page);
$this->assertEquals('<p>This is a rendered placeholder!</p>' . $parent_markup, $output, 'Rendered output as expected, with the placeholder replaced.');
];
$output = $renderer->renderRoot($page);
$this->assertEquals('<p>This is a rendered placeholder!</p>' . $parent_markup, $output, 'Rendered output as expected, with the placeholder replaced.');