I think that according to Understanding the Open Graph Approval Process , each action element on an Open graph has a provision to give steps to reproduce an action while we submit.
Here we can explain the steps in detail, and the test environment can be live / intermediate.
As you said, there are two types of users, you can explain in detail how to change the user type or register as a user type, and then they can test.
As you know, using the application settings, we can create as many test users as possible, and we can also link them in FB. I think that FB will also do the same to test users b / w interactions. The key point is that you explain in detail how to test when submitted.
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