Can/should I submit an early prototype of my device for Zigbee certification testing?
We strongly recommend executing your own functional testing early and often - ideally, using a test harness from an authorized test service provider. That said, it's not necessary to submit your product to a test service provider for official Zigbee Alliance testing until your product design is finalized.
The Zigbee Alliance certification covers the entire product, including buttons, LEDs, enclosure, etc. If there is a chance that you will be changing any of those aspects of your product, our recommendation is to wait until your product is market-ready before submitting it for certification testing. If you find that you need to make a minor change to your product after certifying, the Zigbee Alliance has a procedure in place to help you update your certification.
The full certification process is described in detail here: Zigbee Alliance Certification Process.