We have a big old build that is taking too long to run tests and Im trying to setup parallelism to speed things up. After the configuration, I can see the tests are indeed running in parallel and are much faster but Im running into 2 very strange issues:

• Timestamps for record are set as the same: I have this test that creates two different rows in my database with the created_at column. Later the test picks the latest created one using a order(created_at: :desc).first clause. Running locally it works as expected. Running on CircleCI with parallelism though, both created_at are set to the same value (I printed it) and the test just picks the wrong one. I know I can just also order by id desc, but I would like to understand why is that and how can I avoid it.

• Tests with sleep simply doesn’t work: Again, time related, we have this class that runs a block of code and logs how long it took to run. It is as simple as the following:

 class BenchmarkLog
   class << self
     def benchmark_log(title, description, &block)
       begin
         start_time = Time.now
         yield
       ensure
         ellapsed_time = Time.now - start_time
         Rails.logger.info("#{title} - #{description} - #{ellapsed_time}")
       end
     end
   end
 end

On the test, we simply use a sleep to wait for 1s and check if that worked, like:

    BenchmarkLog.benchmark_log("MyClass", "desired operation") do
      sleep(1)
    end

    expect(log_message).to match(/MyClass - desired operation - 1/)

Oddly enough, when running locally and in CircleCI without parallelism it passes, but when running on circle CI with parallelism it fails with the message:

  expected "MyClass - desired operation - 0.0" to match /MyClass - desired operation - 1/
  Diff:
  @@ -1,2 +1,2 @@
  -/MyClass - desired operation - 1/
  +"MyClass - desired operation - 0.0"

Indicating that the sleep command was simply ignored.

Im running the tests with:

circleci tests glob "spec/{services,controllers}/**/*_spec.rb" | circleci tests run --command="xargs bundle exec rspec --format progress --format RspecJunitFormatter -o ~/rspec/rspec_1.xml" --split-by=timings --timings-type=classname

So, what am I missing on the parallelism that seems to be messing up with these timings?

Thanks!