Add category as class to display posts shortcode

functions.php

/**
 * Add category as class to display posts shortcode
 *
 */
function be_dps_category_class( $classes, $post ) {
	$categories = get_the_terms( $post->ID, 'category' );
	foreach( $categories as $category )
		$classes[] = 'cat-' . $category->slug;
	return $classes;
}
add_filter( 'display_posts_shortcode_post_class', 'be_dps_category_class', 10, 2 );