Generic Identity and Test identity

Hello Everyone,

I'm new on OIM and we are currently installing OIM 8.2 for our client.

In the all IAM solution of our client, they use Generic Identity which is not associed to a particular employee  and Test Identity which is use to make test wirh some application.

Do there a best way to implement these type of identity in OIM ?  May be by using subidentity ? 

Where can I find more informations about subidentity and when they are used ?

Thanks for your advices.