Currently, tempest don't have test cases for the features that require multiple nodes(e.g. migrate, evacuate, VM HA, availability_zone, etc.). 
What I have saw is only 'live migration' tests. But it doesn't run in the gate job. 

This is a proposal for multiple nodes testing enablement so that tempest can cover the features which  require multiple nodes in gate job. 
Some possible discussion about it: 

*Test Environment
All gate jobs run on single node now, we don't have the way to setup multiple nodes.
	* How to setup multiple nodes test evn?
	* Who could own the work  and when it could be done?

How many machines are needed?
	* 2. one hypervisor, one hypervisor + control plane
	* later then do 4 - 2x hypervisor, control, tempest

Constraints for running multi-node cloud:
	* Instances need to be able to run their overlay network between them: e.g. gre needs to work between compute + network-node
	* External addresses need to be spoofable, for floating ips to work
	* Need multiple nodes for the test

Solutions [public cloud test nodes]:
	* VPN between the nodes; run the neutron br-ext against the VPN devices
	* Use planned gearman broker to grab a set of machines at once, once of which is the jenkins/turbo endpoint ?
	* OR
	* Heat? Adopt-stack?
	* OR
	* gearman with many jobs

*Multiple nodes testcases
	* rules for multiple nodes testcases
		* write testcases in both API test and Scenario test ?
		* a new type of attribute (@attr(type=''multi-nodes' ?)
	* create and run the job of multiple nodes testing
		* it's better to run it in the gate