Magento Gift Card Extension – Free Gift for Magento 1.8

As you've mentioned there are 10+ extensions that do this. No extension is going to fulfill your every business rule out of the box - make it yourself!

• Create one 'free' product
• Set their visibility to be 'Not Visibile Individually'
• Set the 100+ custom options on the product
• Create a System > Configuration input field and tab set to manage the ID of the free product (alternatively create a product attribute or attribute set that identifies the product as a free product type). I will use the former as a suggested approach.

Then, create a new block and template to display the custom options from this product:

<?php

class YourCompany_YourModule_Block_Freeproduct extends Mage_Core_Block_Abstract
{

    protected $_freeProduct;

    public function getFreeProduct()
    {
        if(!isset($this->_freeProduct)){
            $id = Mage::getStoreConfig('system/freeproduct/free_product_id');
            $this->_freeProduct = Mage::getModel('catalog/product')->load($id);
        }

        return $this->_freeProduct;
    }

    public function getFreeProductOptions()
    {
        if($product = $this->getFreeProduct()){
            if(!$product->hasOptions()){
                return;
            }

            return $product->getOptions();
        }
    }

}

And make use of getFreeProductOptions in your template/phtml file:

<?php if($options = $this->getFreeProductOptions()): ?>

    <select name="free_product">
        <?php foreach($options as $option): ?>
            <option value="<?php echo $option->getId();?>"><?php echo $option->getTitle(); ?></option>
        <?php endforeach; ?>
    </select>

<?php endif; ?>

You will want to call this block that renders the template from inside a getChildHtml and locate that inside of the <form> element on your theme's catalog/product/view.phtml file. This way, the free_product value comes along for the ride with an add to cart button click.

All you have to do then is create an observer of the cart add postdispatch event and examine the request object. From there you'll have the chosen option id to add to the cart. Voila!

Best of luck!

To perform accurate tests you will need to be making the request that generates and sends a valid token back to the client, so you just need to extract the value from that request before submitting the form.

I'm not familiar with Gatling, but this link gives an example of capturing/sending a CSRF token.