v2 vs v3 returns different uid
First, make sure you have the Polymer CLI installed. Then run polymer serve to serve your application locally.
$ polymer serve
$ polymer build
This will create a build/ folder with bundled/ and unbundled/ sub-folders
containing a bundled (Vulcanized) and unbundled builds, both run through HTML,
CSS, and JS optimizers.
You can serve the built versions by giving polymer serve a folder to serve
from:
$ polymer serve build/bundled
$ polymer test
Your application is already set up to be tested via web-component-tester. Run polymer test to run your application's test suite locally.