tl;dr : Capybara with phantomjs is the fastest solution around
Over the years, I have done my fair share of futzing around with Selenium, and when I took a look at Lebowski a few months ago, I thought I had found a silver bullet. It’s really a clean solution for managing everything around acceptance testing, that is, if you’re going to use Selenium.
So far, Capybara’s DSL is so clean and robust for programmatically defining any user action I’ve come up with. I don’t have any benchmarks to share at this time for vanilla-Capybara tests vs. Capybara w/headless JS (poltergeist) but suffice it to say, I spend noticably less time at the command line.
More to come on how to (acceptance) test your Ember.js apps using Capybara/poltergeist.