Carl
According to Cisco PPDIOO doc you should test in implementation phase -
PPDIOO implementation
There is some confusion though over what you mean by test. When doing a design you often lab it up and you would do some initial testing here to make sure that what you are designing actually works. You do not wait until implementation to make sure your design is actually correct. If you did you would look pretty stupid to your line managers if it didn't. So you should always test the design.
The testing i think you are talking about though is more to do with interoperability with your existing network. And implementation is where this is done. This testing is still done before the new system goes live ie. it is done on the live network but your new system is not actually signed off as fit for pupose until it has been shown to -
1) work with the current network
2) have no adverse impact on the current network
So obviously implementation should be done out of core production hours and the company should be aware, and have agreed to, a certain amount of downtime.
Jon
