Before starting a local cli-ui instance, consider following the contributing guide in order to download all required dependencies of vue-cli's packages.

Just after, you should build once then serve @vue/cli-ui-addon-webpack by running:

cd ../cli-ui-addon-webpack yarn build # just do once yarn serve

Then you start the ui server (based on Apollo):

cd ../cli-ui yarn run apollo 

And then in another terminal, you should serve the ui web app:

yarn run serve 

For running E2E tests, you just need to run:

yarn run test:e2e 

This will open a new Cypress window. You can now run all or specific integration tests.