public function testRatio()
 {
     $eur = Money::EUR(100);
     $sameEur = $this->manager->convert($eur, "EUR");
     $this->assertEquals(Money::EUR(100), $sameEur);
     try {
         $this->manager->convert($eur, "USD");
         $this->assertTrue(false);
     } catch (MoneyException $e) {
         $this->assertTrue(true);
     }
     $this->manager->saveRatio("USD", 1.25);
     $usd = $this->manager->convert($eur, "USD");
     $this->assertEquals(Money::USD(125), $usd);
     $this->manager->saveRatio("CAD", 1.5);
     $cad = $this->manager->convert($usd, "CAD");
     $this->assertEquals(Money::CAD(150), $cad);
 }