Don't repeat testimonials on the same page with multiple views.

no_repeat.php

<?php
/**
 * Set global variable to track posts.
 */
function no_repeat_init() {
	global $testimonials_showing;
	$testimonials_showing = array();
}
add_action( 'wp', 'no_repeat_init' );

/**
 * Add query argument to exclude posts already showing.
 *
 * @param array $args
 *
 * @return array
 */
function no_repeat_query_args( $args ) {
	global $testimonials_showing;
	$args['post__not_in'] = $testimonials_showing;
	return $args;
}
add_filter( 'wpmtst_build_query', 'no_repeat_query_args' );

/**
 * Track posts after being shown.
 */
function no_repeat_get_query() {
	global $testimonials_showing;
	$query = WPMST()->get_query();
	foreach ( $query->posts as $post_object ) {
		$testimonials_showing[] = $post_object->ID;
	}
}
add_action( 'wpmtst_view_rendered', 'no_repeat_get_query' );