public function test_sortable_columns_with_current_ordering() {
    $override_sortable_columns = array(
      'author'   => array( 'comment_author', false ),
      'response' => 'comment_post_ID',
      'date'     => array( 'comment_date', 'asc' ), // We will override this with current ordering.
    );

    // Current ordering.
    $_GET['orderby'] = 'comment_date';
    $_GET['order']   = 'desc';

    // Stub the get_sortable_columns() method.
    $object = $this->getMockBuilder( 'WP_Comments_List_Table' )
      ->setConstructorArgs( array( array( 'screen' => 'edit-comments' ) ) )
      ->setMethods( array( 'get_sortable_columns' ) )
      ->getMock();

    // Change the null return value of the stubbed get_sortable_columns() method.
    $object->method( 'get_sortable_columns' )
      ->willReturn( $override_sortable_columns );

    $output = get_echo( array( $object, 'print_column_headers' ) );

    $this->assertStringContainsString( '?orderby=comment_author&order=asc', $output, 'Mismatch of the default link ordering for comment author column. Should be asc.' );
    $this->assertStringContainsString( 'column-author sortable desc', $output, 'Mismatch of CSS classes for the comment author column.' );

    $this->assertStringContainsString( '?orderby=comment_post_ID&order=asc', $output, 'Mismatch of the default link ordering for comment response column. Should be asc.' );
    $this->assertStringContainsString( 'column-response sortable desc', $output, 'Mismatch of CSS classes for the comment post ID column.' );

    $this->assertStringContainsString( '?orderby=comment_date&order=asc', $output, 'Mismatch of the current link ordering for comment date column. Should be asc.' );
    $this->assertStringContainsString( 'column-date sorted desc', $output, 'Mismatch of CSS classes for the comment date column.' );
  }