Terse, but extremely helpful and well formulated. I'll print these out for further reference ;-) I'd add 4) Continuous integration testing doubling as operations monitoring. I know that this doesn't "really" qualify as testing, but from my experience, it's far easier getting bitten by components not working together than from a screwed component alone. The key here is monitoring and testing business parameters from end to end. It doesn't help you finding out where the bug is, but it lets you know early on if there is one.