New Cluster Testing - Best Practice We've finished setup of a 4-node SQL Server 2005 cluster. We are using Windows 2008 R2 as the underlying OS. 

We are looking for suggestions on a set of tests we could perform to test failover of the SQL Instances?
Not even close to comprehensive, but I'd start with:
1.  Pull the ethernet cable(s) for your public ip interface on your primary/active node.  Confirm the failover.
2.  Pull the SAN fibre cable(s) for your active node. Confirm the failover.
3.  Pull the power cable(s) for you active node.  Confirm the failover.

Those represent the main types of failure that MS Clustering will compensate for in the first place...

I think I'd have my real/prod db detached or offline while I played these games.*