ReferenceError: Can't find variable: Turbolinks

[xionon]

This crops up pretty frequently. Tests will randomly fail because Capybara / Poltergeist hasn't waited long enough for Turbolinks to become available.

In my work, sleep(1) seems to fix the problem. Capybara used to implement a method called wait_until, which would have worked perfectly for this, but it was removed. There are several ways to re-implement this behavior, but before I do that, I'll investigate Capybara's API to see if there are any suitable built-in alternatives.

wait_until ideas and implementations:
http://robots.thoughtbot.com/automatically-wait-for-ajax-with-capybara
https://coderwall.com/p/aklybw
https://gist.github.com/jnicklas/d8da686061f0a59ffdf7

[xionon]

After spending a couple hours on this, I've determined that wait_until isn't going to work.

Using this code:

require "timeout"
def wait_until
  Timeout.timeout(Capybara.default_wait_time) do
    until value = yield
      puts "sleep 0.1, turbolinks #{value}"
      sleep(0.1)
    end
    puts "turbolinks #{value}"
    value
  end
end

# snip...
    wait_until {
      page.evaluate_script('typeof Turbolinks === "object" && typeof Turbolinks.visit === "function"')
    }
    page.execute_script('Turbolinks.visit("/pages/2");')

I still see random ReferenceErrors. Re-running the test with or without the same seed value doesn't reproduce the error.

I tried to see how other people are testing their libraries with Turbolinks, and, as far as I can tell... they're not? Even the official Turbolinks tests are literally just flat .html files with calls to console.log.

The suggested method of dealing with timing problems in Poltergeist like this is apparently to just use sleep.

[xionon]

Fixed via pull request #76