/**
  * Update the core_config_data setting for timestamp from the last test
  * message received. Value should be saved in the most appropriate scope for
  * the store being processed. E.g. if the store is the default store, or has
  * the same AMQP configuration as the default store, the timestamp should be
  * updated in the default scope. If the stores AMQP configuration matches a
  * website level configuration, should be saved within that website's scope.
  * @param ITestMessage $payload
  * @param Mage_Core_Model_Store $store
  * @return Mage_Core_Model_Config_Data
  */
 public function updateLastTimestamp(ITestMessage $payload, Mage_Core_Model_Store $store)
 {
     list($scope, $scopeId) = $this->getScopeForStoreSettings($store);
     return Mage::getModel('core/config_data')->addData(array('path' => $this->_amqpConfigMap->getPathForKey('last_test_message_timestamp'), 'value' => $payload->getTimestamp()->format(self::TIMESTAMP_FORMAT), 'scope' => $scope, 'scope_id' => $scopeId))->save();
 }