Shopify does not send the test parameter when sending request to refund session url

[EddieLuong]

I'm building a payment app and create the refund flow following this document https://shopify.dev/apps/payments/processing-a-refund 

But when i tested i realize that the Shopify does not send the "test" parameter as the description when sending the POST request to my refund session URL

I need this parameter to check whether the payment app is in test mode or not. 

Shopify, please let me know why the "test" parameter is missing?

Thanks