title: Laravel 5.4 Upgrade - ReflectionException: Class session does not exist
body: <p>I updated my local environment to use Laravel 5.4, and in doing so, I can no longer run any tests using phpunit. </p>
  
  <p>The error I am getting is:</p>
  
  <pre><code>ApplicationTest::testEnvironment
  ReflectionException: Class session does not exist
  
  /home/vagrant/Code/Sites/sa4/vendor/laravel/framework/src/Illuminate/Container/Container.php:681
  /home/vagrant/Code/Sites/sa4/vendor/laravel/framework/src/Illuminate/Container/Container.php:565
  /home/vagrant/Code/Sites/sa4/vendor/laravel/framework/src/Illuminate/Foundation/helpers.php:105
  /home/vagrant/Code/Sites/sa4/vendor/laravel/framework/src/Illuminate/Foundation/helpers.php:780
  /home/vagrant/Code/Sites/sa4/tests/TestCase.php:30
  </code></pre>
  
  <p>Anyone know of a solution for this? I've hit a brick wall :(</p>