public function startTest(\PHPUnit_Framework_Test $test)
 {
     if (!$test instanceof ExtendableTestCaseInterface) {
         return;
     }
     $extensions = $test->getExtensionClasses($this->extensions);
     foreach ($extensions as $className) {
         $extension = new $className();
         $test->addExtension($extension);
         if ($extension instanceof TestCaseAwareExtensionInterface) {
             $extension->setTestCase($test);
         }
     }
 }