There is the design doc, which should be the referenece for composing the test-plan for this epic.
The main change here is the setup - creating new VMs, with explicitly setting the MAC address (of primary masquerade? secondaries? primary UDNs? should get clarification) to the one of the "previous" VM in the "previous" namespace.
The tests themselves need to mainly check that the functionality is not regressed - migration, connectivity and such - so the new tests can be based on existing tests.