Author: Asim Liaquat (asimlqt22@gmail.com)
 public function testGetByTitle()
 {
     $xml = file_get_contents(__DIR__ . '/xml/spreadsheet-feed.xml');
     $spreadsheetFeed = new SpreadsheetFeed($xml);
     $this->assertTrue($spreadsheetFeed->getByTitle('Test Spreadsheet') instanceof Spreadsheet);
     $this->assertTrue(is_null($spreadsheetFeed->getByTitle('No Spreadsheet')));
 }
 public function getLastUpdatedAt($spreadsheetName, $worksheetName, $format = 'Y-m-d H:i:s')
 {
     $spreadsheet = $this->spreadsheetFeed->getByTitle($spreadsheetName);
     if (is_null($spreadsheet)) {
         throw new FriendlySpreadSheetException(sprintf('Spreadsheet %s is not found', $spreadsheetName));
     }
     $worksheetFeed = $spreadsheet->getWorksheets();
     $worksheet = $worksheetFeed->getByTitle($worksheetName);
     if (is_null($worksheet)) {
         throw new FriendlySpreadSheetException(sprintf('Worksheet %s is not found', $worksheetName));
     }
     return $worksheet->getUpdated()->format($format);
 }