Ticket #23362: metabox-with-html5-validity-constraints.php

<?php
/**
 * Test metabox for #23362
 * http://core.trac.wordpress.org/ticket/23362
 */
add_action( 'add_meta_boxes', function () {     
        $post_type = 'post';
        $id = 'html5';
        $title = 'Metabox with HTML5 form validation';
        $context = 'normal';
        $priority = 'default';
        $callback_args = null;
        $callback = function () {
                ?>
                <p<label>REQUIRED: <input required></p>
                <p<label>type=email: <input type=email></p>
                <?php
        };
        add_meta_box( $id, $title, $callback, $post_type, $context, $priority, $callback_args );
});