When initializing the SDK, you can hardcode a device ID to send to the API in order to have the same answer all the time (see SDK documentation).
[In Progress] On the Cross-Promotion dashboard side
We are implementing a test mode in the dashboard for you to make all tests possible before going live.
This feature allows you to enable testing device to have ads displayed all the time according to the parameters set in the dashboard.
Meanwhile, you can contact your Key Success Manager to manually enable testers for cross-promotion with a list of IDFVs (or IDFA if you can’t find IDFV).