Information about the techniques to safely deploy at.js to a non-production environment.
In addition to the following information, you can use the Adobe Target VEC Helper browser extension for Google Chrome.
Requestly is a free Chrome extension that lets you redirect requests to an alternate URL.
You deploy at.js to a URL, and then use Requestly to map your current mbox.js file URL to the new at.js URL. Then, any time your website tries to load mbox.js, it loads at.js instead. This approach also make it easier for Adobe to provide support.
If you host mbox.js in your codebase and are able to easily make updates to your code environments, deploy at.js to one of your lower environments.
For better support from Adobe, deploy the file to an environment that Adobe can access.
Charles Web Debugging Proxy is an application available for Mac and Windows whose Map Local feature can be used to map the loading of your production mbox.js file to a local copy of at.js. A free trial version is available for download for Mac and Windows.
Fiddler is a similar tool available as a free download for Windows.
If you are using another tag manager, it probably has a way to deploy at.js safely without impacting your production traffic.