my-testimonial-count.php

/**
 * A shortcode to display the number of testimonials.
 *
 * For Strong Testimonials plugin.
 *
 * For all: [my_testimonial_count]
 * For a specific category (by slug): [my_testimonial_count category="abc"]
 *
 * @param      $atts
 * @param null $content
 *
 * @return int
 */
function my_testimonial_count( $atts, $content = null ) {
	$atts = shortcode_atts(
		array(
			'category' => '',
		),
		$atts
	);

	$args = array(
		'posts_per_page'           => -1,
		'post_type'                => 'wpm-testimonial',
		'post_status'              => 'publish',
		'wpm-testimonial-category' => $atts['category'],
		'suppress_filters'         => true,
	);
	$posts_array = get_posts( $args );

	return count( $posts_array );
}
add_shortcode( 'my_testimonial_count', 'my_testimonial_count' );