Looping Through Categories of a CPT

I am trying to create tabs using the Foundations framework, outputting posts from a custom post type called testimonial and filtering them through their assigned custom category called filed-under. What am I doing wrong in my loop?

What I Have Working

• Category tabs appear when new categories are created

What is Not Working

• The posts aren't appearing in the tabbed content area
• How do you get the loop to filter the 'all' category?

Link to Demo http://staging-newmummycompanyca.temp312.kinsta.cloud/testimonials/

Code

        ?php
        // TABBED HEADERS
        echo 'ul class=tabs data-tabs id=example-tabs';
        echo 'li class=tabs-title is-active link-no-style';
        echo 'a href=#all aria-selected=trueAll/a';
        echo '/li';
        $args = array(
          'hide_empty' = 1,
          'orderby'   = 'name',
          'order'     = 'ASC',
          'post_type' = 'testimonial',
          'taxonomy'  = 'filed-under',
        );
        $categories = get_categories($args);
        foreach ($categories as $category) {
          echo
            'li class=tabs-title link-no-style
                a href=#' . $category-slug . ' aria-selected=true role=tab data-toggle=tab    
                  ' . $category-name . '
                /a
              /li';
        }
        echo '/ul';

        // TABBED CONTENT
        echo 'div class=tabs-content data-tabs-content=example-tabs';
        echo 'div class=tabs-panel is-active id=' . $category-slug . '';
        echo 'ul class=accordion data-accordion data-allow-all-closed=true';
        foreach ($categories as $category) {
          $the_query = new WP_Query(array(
            'post_type'     = 'testimonial',
            'post_status'   = 'publish',
            'category_name' = $category-slug,
          ));
          while ($the_query-have_posts()) : $the_query-the_post();
            echo 'li class=accordion-item data-accordion-item';
            echo 'a href=# class=accordion-titlep';
            the_title();
            echo '/p/a';
            echo 'div class=accordion-content data-tab-content';
            echo the_field('testimonial');
            echo '/div';
            echo '/li';
          endwhile;
          wp_reset_postdata();
        }
        echo '/ul';
        echo '/div';
        echo '/div';
        ?

CODE V2

?php 
        echo 'ul class=tabs data-tabs id=example-tabs';
        echo 'li class=tabs-title is-active link-no-style';
        echo 'a href=# aria-selected=trueAll/a';
        echo '/li';  

        $_terms = get_terms(array('filed-under'));
        foreach ($_terms as $term) {

        // TABBED HEADERS 
        echo 'li class=tabs-title link-no-style';
        echo 'a href=#' . $term-slug . 'aria-selected=true role=tab data-toggle=tab';
        echo $term-name;
        echo '/a';
        echo '/li';
        }  // CLOSE OFF FIRST LOOP 
        echo '/ul';

        foreach ($_terms as $term) :
        $term_slug = $term-slug;
        
        // QUERY
        $_posts = new WP_Query( array(
          'post_type'         = 'testimonial',
          'posts_per_page'    = -1, 
          'tax_query' = array(
            array(
              'taxonomy' = 'filed-under',
              'field'    = 'slug',
              'terms'    = $term_slug,
            ),
          ),
        )); 
        
        // TABBED CONTENT
        echo 'div class=tabs-content data-tabs-content=example-tabs';
        echo 'div class=tabs-panel id=' . $term_slug . '';
        echo 'ul class=accordion data-accordion data-allow-all-closed=true';
        if( $_posts-have_posts() ) :  while ( $_posts-have_posts() ) : $_posts-the_post(); 
        echo 'li class=accordion-item data-accordion-item';
        echo 'a href=# class=accordion-title';
        echo 'p';
        the_title(); 
        echo '/p';
        echo '/a';
        echo 'div class=accordion-content data-tab-content';
        echo the_field('testimonial');
        echo '/div';
        echo '/li'; 
        endwhile; endif; wp_reset_postdata();
        echo '/ul';
        echo '/div';
        echo '/div';
        endforeach; 
        ?