Thank you for reaching us out. I am Sherwin from Google Ads API support team. I hope that you are doing well today.
Moving forward to your concern, there is no test GCLID because it can be created if you have a Production Account. The Test accounts do not serve authentic ads so you will not get any GCLID. With that being said, in order for you to get a GLID, we suggest to create a production Google Ads Manager account, you may visit this
link. Thank you for your understanding.