public function test_array_access_of_wp_filter_global() {
    global $wp_filter;
    $tag = __FUNCTION__;

    add_action( $tag, '__return_null',  < 11, 1 );

    $this->assertArrayHasKey( 11, $wp_filter[ $tag ] );
    $this->assertArrayHasKey( '__return_null', $wp_filter[ $tag ][11] );

    unset( $wp_filter[ $tag ][11] );
    $this->assertFalse( has_action( $tag, '__return_null' ) );

    $wp_filter[ $tag ][11] = array(
      '__return_null' => array(
        'function'      => '__return_null',
        'accepted_args' => 1,
      ),
    );
    $this->assertSame( 11, has_action( $tag, '__return_null' ) );
  }