Allow time to be frozen

[sos4nt]

SitePrism's wait_until_true won't work when freezing time via Timecop.freeze or Rails' travel_to. If you try to do so, a FrozenInTimeError will be raised.

This commit removes the Time#now dependency and utilizes sleep instead, which doesn't have such restrictions.

[sos4nt]

Travis shows one minor failure:

  Scenario: Load a Page that has load validations set # features/navigation.feature:32
    When I navigate a page with load validations      # features/step_definitions/navigation_steps.rb:65
    Then I am made to wait to continue                # features/step_definitions/navigation_steps.rb:80
      expected: > 0.2
           got:   0.195541809 (RSpec::Expectations::ExpectationNotMetError)

I assume this is because the new wait_until_true returns slightly faster. Maybe you could take a look into it and adjust the threshold accordingly.

[luke-hill]

This is going to take a bit of time to look into. As I remember distinctly the person who fixed this showed that it helped things a bit.

Undoing / altering this change feels a bit scary and I don't really use Timecop much. If you want to help / offer some more indepth stuff, that might help get this merged quickly.

As for the timeouts, don't worry about those. There are 3-5 tests that are flaky, I do mean to fix them up, but I'm lazy and I've not dedicated enough time to this project in the last 2-3 months. I need to get back on board!

In terms of "accepting" it though, it seems ok enough, just want to make sure we alter it in a way that won't nark it for others.

[luke-hill]

Code style tweaks:
Remove in-line disabling of cops (I want to get all the cops fixed up, again another chore for me) - See if you can refine the logic to not peeve off rubocop.
Add changelog entry. Mention you are refining existing logic to allow Rails users to use travel_to.

[sos4nt]

See if you can refine the logic to not peeve off rubocop.

I've extracted the whole timer thread handling into a separate Timer class which greatly simplified the wait_until_true method.

Add changelog entry.

Done.

If you want to help / offer some more indepth stuff, that might help get this merged quickly.

The former approach polled Time.now in a loop to calculate if the method's runtime exceeded wait_time seconds:

loop do
  return true if yield
  break if Time.now - start_time > wait_time
  # ...
end     

This obviously doesn't work if Time.now is stubbed in a way that it returns the same value every time. (the way travel_to and Timecop.freeze work)

In my new approach, I'm starting a separate timer thread. The thread just sleeps for wait_time seconds and then sets a done flag:

@thread = Thread.start do
  sleep wait_time
  @done = true
end

The main thread uses a loop, just like before. But instead of checking Time.now, it now checks the timer's done flag:

loop do
  return true if yield
  break if timer.done?
  # ...
end

The huge difference is that sleep doesn't rely on Ruby's Time class. It uses C functions to suspend the timer thread for the given duration.

Note that the timer thread just sets the done flag. It doesn't interrupt the main thread in any way.

[sos4nt]

FYI: I'm going to push some minor changes (the timer spec lacks some cleanup)

[sos4nt]

Spec is fixed now. I've also rebased the PR.

[ineverov]

@sos4nt @luke-hill We can just replace Time.now with Process.clock_gettime(Process::CLOCK_MONOTONIC) (ruby 2.1+) and avoid a bunch of refactoring. What do you think?

[sos4nt]

@ineverov to me, using sleep looks cleaner than polling the current time.

It might also be safer than using a method that Timecop might mock in the future: travisjeffery/timecop#220

[luke-hill]

As for using one method over the other, I'm kind of agnostic, this enhances the gem so I'm fine with it as is, and if someone comes along later we can tweak it further.

[temochka]

@luke-hill would it be possible to cut a new gem version that includes this fix please? 🙏

[luke-hill]

@temochka One will be cut in rubygems in the next 24hours.

[temochka]

Thank you @luke-hill! This is great news 🙌