One thing I am thinking about due to the VCDX application is operational readiness. What does it mean to pronounce this project or solution good-to-go? In my world it would be to test that each feature does exactly what it should be doing. Most commonly this will be failover testing, but could reach into any feature or be as big as DR plan that involves much more than the technical parts doing what they should. Some things I think need to be checked:
Are the CPU, Memory, Network and Storage doing what they should be? Some load generating programs like IOmeter can be fine to test network and storage performance. CPU busy programs can verify Resource Pools and DRS are behaving the way they should.
You have redundant links right? Start pulling cables. Do the links failover for Virtual Machines, Service Console, and iSCSI? How about the redundancy of the physical network, even more cable to pull! Also test that the storage controllers failover correctly. Also, I will make sure HA does what it is supposed to, instantly power off a host and make sure some test virtual machines start up somewhere else on the cluster.
Virtual Center Operations
Deploy new virtual machines, host and storage VMotion, deploy from a template, and clone a vm are all things we need to make sure are working. If this is a big enough deployment make sure the customer can use the deployment appliance if you are making use of one. Make sure the alarms send traps and emails too.
Create new luns, test replication, test storage alarms and make sure the customer understands thin provisioning if it is in use. Make sure you are getting IO as designed from the Storage side. Making use of the SAN tools to be sure the storage is doing what it should.
You can verify that each application is working as intended within the virtual environment.
There must be something I am missing but the point is trying to test out everything so you can tell that this virtualization solution is ready to be used.