EShoppingCart::put PHP Method

    public function put(IECartPosition $position, $quantity = 1)
    {
        $key = $position->getId();
        if ($this->itemAt($key) instanceof IECartPosition) {
            $position = $this->itemAt($key);
            $oldQuantity = $position->getQuantity();
            $quantity += $oldQuantity;
        }
        $this->update($position, $quantity);
        $this->eventManager->fire(CartEvents::CART_ADD_ITEM, new CartEvent(Yii::app()->getUser(), $this));
    }

 function testEmpty()
 {
     $this->setUp();
     $cart = new EShoppingCart();
     $this->assertTrue($cart->isEmpty());
     $book = Book::model()->findByPk(1);
     $cart->put($book);
     $this->assertFalse($cart->isEmpty());
 }