How to make my taxonomy URL work?

I register my taxonomy ( Writer ) with this code :

function writer() {

  $labels = array(
    'name'                       => 'writer',
    'singular_name'              => 'writer',
    'menu_name'                  => 'writers',
    'all_items'                  => 'show all',
    'parent_item'                => 'parent',
    'parent_item_colon'          => 'parent:',
    'new_item_name'              => 'add new writer',
    'add_new_item'               => 'add',
    'edit_item'                  => 'edit',
    'update_item'                => 'update',
    'separate_items_with_commas' => 'separate with comma',
    'search_items'               => 'search',
    'add_or_remove_items'        => 'add/remove',
    'choose_from_most_used'      => 'most used',
    'not_found'                  => 'not found',
  );
  $args = array(
    'labels'                     => $labels,
    'hierarchical'               => true,
    'public'                     => true,
    'show_ui'                    => true,
    'show_admin_column'          => true,
    'show_in_nav_menus'          => true,
    'show_tagcloud'              => true,
    'rewrite'                    => array('slug' => 'writer'),
  );
  register_taxonomy( 'writer', array( 'books_type' ), $args );

}
add_action( 'init', 'writer', 0 );

and i made a file with taxonomy-writer.php name in my theme directory. And i can access my taxonomies with URLs like this :

http://localhost/test/writer/ala-alam-falaki

But the problem is, when i try this URL :

http://localhost/test/writer/

I get 404, why can't i access this page ? what is the problem ?