"Remote destinations must be Time Division Multiplex (TDM) devices or off-system IP phones on other clusters or systems. You cannot configure IP phones within the same Unified CM cluster as remote destinations. "So if you'd like to test mobility feature without involving PSTN gateways, you may build another CUCM cluster (with VMWare, it should be just another VM). Then you may create ICT (Inter-Cluster Trunk) between two clusters. You may use the IP phones on another clusters as "Remote Destination". With this setup, you may test the following features:
1) Mobile Connect (SNR)
2) Enterprise Feature Access (EFA)
You won't be able to test the following feature:
MVA (Mobile Voice Access), because it requires IVR function of the voice gateway.
If you have a voice gateway but does not have T1/PRI, you may use CME to simulate PSTN phones.