如何为自定义推荐帖子类型添加精选图片支持

I am creating a Testimonials custom post type. but I am not getting fetured image support for the same.. I am getting in all the posts and pages . I had also include the support in register_post_type() function. Following is my code: I am calling add theme support function above this

I am creating custom theme in WordPress.

add_action( 'init', 'testimonials_post_type' );
function testimonials_post_type() {
    $labels = array(
        'name' => 'Testimonials',
        'singular_name' => 'Testimonial',
        'add_new' => 'Add New',
        'add_new_item' => 'Add New Testimonial',
        'edit_item' => 'Edit Testimonial',
        'new_item' => 'New Testimonial',
        'view_item' => 'View Testimonial',
        'search_items' => 'Search Testimonials',
        'not_found' =>  'No Testimonials found',
        'not_found_in_trash' => 'No Testimonials in the trash',
        'parent_item_colon' => '',
    );
 register_post_type( 'testimonials', array(
        'labels' => $labels,
        'public' => true,
        'publicly_queryable' => true,
        'show_ui' => true,
        'exclude_from_search' => true,
        'query_var' => true,
        'rewrite' => true,
        'capability_type' => 'post',
        'has_archive' => true,
        'hierarchical' => false,
        'menu_position' => 10,
        'supports' => array( 'editor','thumbnail' ),
        'register_meta_box_cb' => 'testimonials_meta_boxes',
    ) );
}