Capybara 3.12.0 + Puma 3.10.0 + TimeCop Fix

reactor.rb

module CoreExtensions
  module Puma
    module Reactor
      def calculate_sleep
        if @timeouts.empty?
          @sleep_for = ::Puma::Reactor::DefaultSleepFor
        else
          diff = @timeouts.first.timeout_at.to_f - Time.now.to_f

          if diff < 0.0
            @sleep_for = 0
          elsif diff > 60
            @sleep_for = ::Puma::Reactor::DefaultSleepFor
          else
            @sleep_for = diff
          end
        end
      end
    end
  end
end

spec_helper.rb

# Fix Puma + TimeCop issue https://github.com/puma/puma/issues/1582
require 'puma/reactor'
Puma::Reactor.prepend CoreExtensions::Puma::Reactor

Will this be included in a new release soon?

You should pull in global ::Time.now.to_f otherwise this clashes with CoreExtensions::Time which has no now method:

Error reached top of thread-pool: undefined method `now' for CoreExtensions::Time:Module (NoMethodError)
Error in reactor loop escaped: undefined method `now' for CoreExtensions::Time:Module (NoMethodError)
/work/YetAnotherCryptoApp/spec/support/reactor.rb:12:in `calculate_sleep'

Original issue described here: puma/puma#1582

This is no longer an issue in Puma 4.x