This gist demonstrates how to build a basic testimonials fade in and fade out.

slider.js

jQuery(document).ready(function($){
	var testimonials = $('aside .testimonials .testimonial');
	var current = 0;

	function slide(){
	intv = setInterval(function() {
		$(testimonials[current]).fadeOut('slow', function(){
			if( typeof testimonials[current+1] != 'undefined') {
					current += 1;
					
			} else {
				current = 0;
			}

			$(testimonials[current]).fadeIn('slow');
		});
	}, 5000 );       
	}
	slide();
});

style.scss

.testimonials {
	.testimonial {
		display: none;

		&:first-child {
			display: inline;
		}
	}
}

testimonials.php

<div class="testimonials">
	<?php 
		$testimonials = new WP_Query(
			array(
				'post_type' => 'testimonials',
				'posts_per_page' => -1
			)
		);

		if ( $testimonials->have_posts() ): 
		 	while( $testimonials->have_posts() ): $testimonials->the_post(); ?>
				<div class="testimonial"> 
					<?php 
					$meta = get_post_meta($post->ID);
					echo '<p class="test">'.get_the_content().'</p>';
					echo '<p class="meta">'.get_the_title().'<br>'.$meta['_testimonial_title'][0].'<br>'.$meta['_testimonial_company'][0].'</p>';?>
				</div>
			<?php endwhile;
		endif;
	?>
</div>