Update TestInit.php for new autoloading stuff

This patch took inspiration from and has similarities to: https://github.com/doctrine/doctrine2/blob/master/tests/Doctrine/Tests/TestInit.php

tests/Doctrine/Tests/TestInit.php

@@ -6,8 +6,16 @@ namespace Doctrine\Tests;
 
 error_reporting(E_ALL | E_STRICT);
 
-require_once __DIR__ . '/../../../vendor/autoload.php';
-
-$classLoader = new \Doctrine\Common\ClassLoader('Doctrine\Tests', __DIR__ . '/../../');
-$classLoader->register();
+if (file_exists(__DIR__ . '/../../../vendor/autoload.php')) {
+    // dependencies were installed via composer - this is the main project
+    $classLoader = require __DIR__ . '/../../../vendor/autoload.php';
+} elseif (file_exists(__DIR__ . '/../../../../../autoload.php')) {
+    // installed as a dependency in `vendor`
+    $classLoader = require __DIR__ . '/../../../../../autoload.php';
+} else {
+    throw new \Exception('Can\'t find autoload.php. Did you install dependencies via composer?');
+}
 
+/* @var $classLoader \Composer\Autoload\ClassLoader */
+$classLoader->add('Doctrine\\Tests\\', __DIR__ . '/../../');
+unset($classLoader);