WooCommerce custom ShortCodes

I am trying to create a custom shortcode for WooCommerce, I want to display featured products from a specific catagory at the end of a post.

There is a standard shortcode:

[featured_products per_page="12" columns="4" orderby="date" order="desc"]

I want to add catagory to this, so the new shortcode will be:

[featured_category_products category="13" per_page="4" columns="4" orderby="date" order="desc"]

To get it work it’s officiously necessary to create a function for it, so I found the class-wc-shortcodes.php file with all the default shortcodes.

I add a new function based on the default featured product:

public function featured_category_products( $atts ) {

    global $woocommerce_loop;

    extract(shortcode_atts(array(
        'category'      => '',
        'per_page'  => '4',
        'columns'   => '4',
        'orderby' => 'date',
        'order' => 'desc'
    ), $atts));

    $args = array(
        'post_type' => 'product',
        'post_status' => 'publish',
        'ignore_sticky_posts'   => 1,
        'posts_per_page' => $per_page,
        'orderby' => $orderby,
        'order' => $order,
        'meta_query' => array(
            array(
                'key' => '_visibility',
                'value' => array('catalog', 'visible'),
                'compare' => 'IN'
            ),
            array(
                'key' => '_featured',
                'value' => 'yes'
            )
        ),
        'tax_query'             => array(
            array(
                'taxonomy'      => 'product_cat',
                'terms'         => array( esc_attr($category) ),
                'field'         => 'slug',
                'operator'      => 'IN'
            )
        )
    );

    ob_start();

    $products = new WP_Query( $args );

    $woocommerce_loop['columns'] = $columns;

    if ( $products->have_posts() ) : ?>     

        <?php woocommerce_product_loop_start(); ?>

            <?php while ( $products->have_posts() ) : $products->the_post(); ?>

                <?php woocommerce_get_template_part( 'content', 'product' ); ?>

            <?php endwhile; // end of the loop. ?>

        <?php woocommerce_product_loop_end(); ?>

    <?php endif;

    wp_reset_postdata();

    return '<div class="woocommerce">' . ob_get_clean() . '</div>';
}

I added the category variable extraction (and checked if it worked) and added tax-query part (found it from another function that show product based on categories). So I thought this should work, but off course not. I don’t get any results nor a error.

Anybody an idea how the get this to work?