According to the codex category_name only takes one string value. category_in accepts an array of category IDs:
<?php
$args = array(
'category__in' = array(1,4,6,8), // use IDs
'post_type'=> array( $ptype, 'post', 'test-btum', 'test-other' )
);
$wp_query = new WP_Query($args); ?>
It might be possible that the default category taxonomy is not registered to your custom post type. In that case try adding
register_taxonomy_for_object_type( 'category', 'test-btum' )
to your themes functions.php. Repeat for every post type you want to register. Make sure your custom post types are actually assigned to a category otherwise they won’t show up in your query.