vaadin test elements
First, make sure you have the Polymer CLI installed. Then run polymer serve to serve your application locally.
$ polymer serve --hostname 0.0.0.0
$ polymer build
This will create builds of your application in the build/ directory, optimized to be served in production. You can then serve the built versions by giving polymer serve a folder to serve from:
$ polymer serve build/default
$ 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.