Mixed domains are domains where there are host controllers with different versions. On mixed domain transformer tests are required to allow the domain controller to talk to legacy host controllers.

About stability levels, Domain mode only works for paired stability levels, E.g DC community – Secondary HC community, preview – preview, default – default ... and so on. It is necessary to test the feature in domain mode. However, we do not distinguish between mixed domains and standard domains.

We think transformer tests for features under preview and experimental can be safely avoided, so the task here is to reject the registration of host controllers when they are running on different versions and the DC is on preview or experimental.