Before migrating the content try this step. this will save lot of your time.
First get the correct AD credentail which you are using in PROD Env and configure the Test AD plugin in the same way.
Add the same group manually in the Test Env and update the AD plugin with the option ""create a new aliase" checked.
Observe the users and groups getting created in usres and group section.
Now got to the Authenticaion tab and remove the AD group and update at the bottom.
let me know if you get any error after that.