your demo not working

[flik]

/d/xampp/htdocs/php-webdriver-demo-master

$ vendor/bin/phpunit ./tests/GitHubTest.php PHPUnit 3.7.28 by Sebastian Bergmann.

Configuration read from D:\xampp\htdocs\php-webdriver-demo-master\phpunit.xml

Fatal error: Uncaught Error: Call to a member function quit() on null in D:\xamp p\htdocs\php-webdriver-demo-master\tests\GitHubTest.php:22 Stack trace: #0 D:\xampp\htdocs\php-webdriver-demo-master\vendor\phpunit\phpunit\PHPUnit\Fram ework\TestCase.php(870): GitHubTest->tearDown() #1 D:\xampp\htdocs\php-webdriver-demo-master\vendor\phpunit\phpunit\PHPUnit\Fram ework\TestResult.php(648): PHPUnit_Framework_TestCase->runBare() #2 D:\xampp\htdocs\php-webdriver-demo-master\vendor\phpunit\phpunit\PHPUnit\Fram ework\TestCase.php(783): PHPUnit_Framework_TestResult->run(Object(GitHubTest)) #3 D:\xampp\htdocs\php-webdriver-demo-master\vendor\phpunit\phpunit\PHPUnit\Fram ework\TestSuite.php(775): PHPUnit_Framework_TestCase->run(Object(PHPUnit_Framewo rk_TestResult)) #4 D:\xampp\htdocs\php-webdriver-demo-master\vendor\phpunit\phpunit\PHPUnit\Fram ework\TestSuite.php(745): PHPUnit_Framework_TestSuite->runTest(Object(GitHubTest ), Object(PHPUnit_Framework_TestResult)) #5 D:\xampp\htdocs\php-webdriver-demo-master\vendor\phpunit\phpunit\PHPUnit\ in D:\xampp\htdocs\php-webdriver-demo-master\tests\GitHubTest.php on line 22 PHP Fatal error: Uncaught Error: Call to a member function quit() on null in D: \xampp\htdocs\php-webdriver-demo-master\tests\GitHubTest.php:22 Stack trace: #0 D:\xampp\htdocs\php-webdriver-demo-master\vendor\phpunit\phpunit\PHPUnit\Fram ework\TestCase.php(870): GitHubTest->tearDown() #1 D:\xampp\htdocs\php-webdriver-demo-master\vendor\phpunit\phpunit\PHPUnit\Fram ework\TestResult.php(648): PHPUnit_Framework_TestCase->runBare() #2 D:\xampp\htdocs\php-webdriver-demo-master\vendor\phpunit\phpunit\PHPUnit\Fram ework\TestCase.php(783): PHPUnit_Framework_TestResult->run(Object(GitHubTest)) #3 D:\xampp\htdocs\php-webdriver-demo-master\vendor\phpunit\phpunit\PHPUnit\Fram ework\TestSuite.php(775): PHPUnit_Framework_TestCase->run(Object(PHPUnit_Framewo rk_TestResult)) #4 D:\xampp\htdocs\php-webdriver-demo-master\vendor\phpunit\phpunit\PHPUnit\Fram ework\TestSuite.php(745): PHPUnit_Framework_TestSuite->runTest(Object(GitHubTest ), Object(PHPUnit_Framework_TestResult)) #5 D:\xampp\htdocs\php-webdriver-demo-master\vendor\phpunit\phpunit\PHPUnit\ in D:\xampp\htdocs\php-webdriver-demo-master\tests\GitHubTest.php on line 22

feb2018@adminxA MINGW32 /d/xampp/htdocs/php-webdriver-demo-master