code: public function invoke($method)
      {
          $queue = $this->createErrorQueue();
          set_error_handler('SimpleTestErrorHandler');
          parent::invoke($method);
          restore_error_handler();
          $queue->tally();
      }
docs: Invokes a test method and dispatches any untrapped errors.
  Called back from the visiting runner.
  
  @param string $method    Test method to call.