/**
  * Invokes factory method to instantiates a new Exchange Service
  * 
  * @param object|string|null $service The exchange service used for getting exchange rate
  * @return CurrencyExchange\Exchanger
  */
 public function setService($service = null)
 {
     $this->_service = ServiceFactory::factory($service);
     return $this;
 }
 public function testServiceFactoryInstantiatesYahooFinanceServiceAsDefault()
 {
     $instance = ServiceFactory::factory();
     return $this->assertInstanceOf('\\CurrencyExchange\\Service\\YahooFinance', $instance);
 }