I’m a big fan of Chimp for UI testing, it’s just stupid simple. It comes with everything you need: includes its own selenium standalone and chromedriver, different test runner frameworks options (mocha, jasmine, cucumber), assertion libraries, and it has some Meteor-specific stuff.
I’m using CircleCI for builds, (which is a great service), you can see my CircleCI config file here for running unit tests and UI tests. The tests are running against a headless Chrome.
In that CircleCI config file, I’m just using the meteor command to spin up a local dev server and run UI tests against it with Chimp, but you could easily modify the workflow to run unit tests, then deploy your app to a preprod server, then run UI tests against that.