title: Setting process isolation to false in phpunit.xml causes Laravel Functional Tests to fail
body: <p>On our previous app, using Laravel 5.3, setting <code>processIsolation</code> to false sped up our tests without causing any errors:</p>
  
  <pre><code>phpunit.xml:
  &lt;phpunit backupGlobals="false"
       ...
       processIsolation="false"
       stopOnFailure="false"&gt;
  </code></pre>
  
  <p>On our current project, in laravel 5.4, setting <code>processIsolation</code> to false causes all of our functional tests to fail (though they are indeed faster) (some removed for brevity):</p>
  
  <pre><code>5) Tests\Feature\CallsToActionApiControllerTest::testUsers
  Symfony\Component\HttpKernel\Exception\NotFoundHttpException:
  /johnny/vendor/laravel/framework/src/Illuminate/Routing/RouteCollection.php:161
  /johnny/vendor/laravel/framework/src/Illuminate/Routing/Router.php:533
  /johnny/vendor/laravel/framework/src/Illuminate/Routing/Router.php:512
  /johnny/vendor/laravel/framework/src/Illuminate/Routing/Router.php:498
  /johnny/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php:174
  /johnny/vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php:30
  /johnny/vendor/barryvdh/laravel-cors/src/HandleCors.php:34
  /johnny/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php:148
  ...
  /johnny/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php:102
  /johnny/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php:149
  /johnny/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php:116
  /johnny/vendor/laravel/framework/src/Illuminate/Foundation/Testing/Concerns/MakesHttpRequests.php:234
  /johnny/vendor/laravel/framework/src/Illuminate/Foundation/Testing/Concerns/MakesHttpRequests.php:206
  /johnny/tests/Functional/CallsToAction/CallsToActionApiControllerTest.php:142
  
  ...
  7) Tests\Feature\EmailEndpointControllerTest::testCaptureEventsWithBlankRequest
  Expected status code 200 but received 404.
  Failed asserting that false is true.
  
  /johnny/vendor/laravel/framework/src/Illuminate/Foundation/Testing/TestResponse.php:55
  /johnny/tests/Functional/Email/EmailActionApiControllerTest.php:88
  
  8) Tests\Feature\EmailEndpointControllerTest::testUnsubscribe
  Expected status code 200 but received 404.
  Failed asserting that false is true.
  
  /johnny/vendor/laravel/framework/src/Illuminate/Foundation/Testing/TestResponse.php:55
  /johnny/tests/Functional/Email/EmailActionApiControllerTest.php:96
  
  9) Tests\Feature\EmailEndpointControllerTest::testUnsubscribeWithAlreadyUnsubscribedEmail
  Expected status code 200 but received 404.
  Failed asserting that false is true.
  
  /johnny/vendor/laravel/framework/src/Illuminate/Foundation/Testing/TestResponse.php:55
  /johnny/tests/Functional/Email/EmailActionApiControllerTest.php:108
  
  ERRORS!
  Tests: 72, Assertions: 79, Errors: 21, Failures: 9.
  Script ./vendor/bin/phpunit handling the test event returned with error code 2
  </code></pre>
  
  <p>They are all 404 errors, or NotFoundHttpException errors.</p>
  
  <p>Our working earlier project was laravel 5.3 and phpunit 5.5; our current broken project is laravel 5.4 and phpunit 5.7. I noticed one change between the two laravels was that the application URL in <code>app.php</code> changed from</p>
  
  <pre><code>'url' =&gt; 'http://localhost'
  </code></pre>
  
  <p>to</p>
  
  <pre><code>'url' =&gt; env('APP_URL', 'http://localhost'),
  </code></pre>
  
  <p>But changing it back didn't do anything. Please help -- our tests take 10 minutes instead of 10 seconds.</p>