Here's an easy way to test cluster failover without actually taking down a server. The idea is to fool your client into thinking the server is not available.
Create a new location document in your personal address book. This new location will not contain any cached server addresses. Then, create a new LAN connection document in your personal address book for a server in the cluster. Specify a non-working IP address for the server, and associate the connection with your new location document.
Switch to your new location document and access the server. The bad IP address will fool your client into thinking the server is down, and you'll fail over to another cluster member.