Cucumber + Capybara + Selenium firefox opens example.com not my app
OK, got it working. Here's what I did.
env.rb added:
require "selenium-webdriver"
and changed my steps with 'visit root_url' to:
visit root_path
I think that's everything I changed.
I honestly thought I'd tried that (and every other permutation of every other issue/fix I've seen). Can't believe I've wasted 3 days on this then found the answer just hours after posting the question publicly.