VMware vCenter Simulator
VMware vCenter Simulator (VCSIM) is an unsupported tool from VMware that is included with the vCenter Server Appliance (vCSA) and is used to simulate changes in a vSphere environment for testing and development purposes.
With VCSIM, the user can modify vSphere inventory to simulate a large number of virtual machines, ESXi hosts, and change the data store configuration.
To access VCSIM, the user needs to deploy vCSA, then use a SSH client to connect to vCSA or use the Virtual Appliance Management Infrastructure interface.
VMware introduced VCSIM in vCSA 5.1.