public function testGlobalTiers()
 {
     $t1 = new PriceTier(array('MinQty' => 20, 'Percentage' => 0.5, 'SiteConfigID' => SiteConfig::current_site_config()->ID));
     $t1->write();
     $tiers = $this->p1->getPrices();
     $this->assertEquals(2, $tiers->count());
     $price1 = 27.5;
     $qty1 = 19;
     $price2 = round(27.5 * 0.5, 2);
     $qty2 = 20;
     ShoppingCart::singleton()->add($this->p1, $qty1);
     ShoppingCart::curr()->calculate();
     $this->assertEquals($price1 * $qty1, ShoppingCart::curr()->SubTotal());
     ShoppingCart::singleton()->setQuantity($this->p1, $qty2);
     ShoppingCart::curr()->calculate();
     $this->assertEquals($price2 * $qty2, ShoppingCart::curr()->SubTotal());
 }