Flatware

Flatware parallelizes your test suite to significantly reduce test time.

Flatware

Add the runners you need to your Gemfile:

gem 'flatware-rspec', require: false    # one
gem 'flatware-cucumber', require: false # or both

then run

bundle install

Usage

Cucumber

To run your entire suite with the default cucumber options, add the flatware-cucumber gem and just:

$ flatware cucumber

RSpec

To run your entire suite with the default rspec options add the flatware-rspec gem and just:

$ flatware rspec

The rspec runner can balance worker loads, making your suite even faster.

It forms balanced groups of spec files according to their last run times, if you've set example_status_persistence_file_path in your RSpec config.

For this to work the configuration option must be loaded before any specs are run. The .rspec file is one way to achieve this:

--require spec_helper

But beware, if you're using ActiveRecord in your suite you'll need to avoid doing things that cause it to establish a database connection in spec_helper.rb. If ActiveRecord connects before flatware forks off workers, each will die messily. All of this will just work if you're following the recommended pattern of splitting your helpers into spec_helper and rails_helper. Another option is to use the configurable hooks.

Options

If you'd like to limit the number of forked workers, you can pass the 'w' flag:

$ flatware -w 3

You can also pass most cucumber/rspec options to Flatware. For example, to run only features that are not tagged 'javascript', you can:

$ flatware cucumber -t 'not @javascript'

Additionally, for either cucumber or rspec you can specify a directory:

$ flatware rspec spec/features

Typical Usage in a Rails App

Add the following to your config/database.yml:

test:
  database: foo_test

becomes:

test:
  database: foo_test<%=ENV['TEST_ENV_NUMBER']%>

Run the following:

$ rake db:setup # if not already done
$ flatware fan rake db:test:prepare

Now you are ready to rock:

$ flatware rspec && flatware cucumber

Faster Startup With ActiveRecord

Flatware has a couple lifecycle callbacks that you can use to avoid booting your app over again on every core. One way to take advantage of this via a spec/flatware_helper.rb file like so:

##
# uncomment if you get a segmentation fault from the "pg" gem
# @see https://github.com/ged/ruby-pg/issues/311#issuecomment-1609970533
# ENV["PGGSSENCMODE"] = "disable"

Flatware.configure do |conf|
  conf.before_fork do
    require 'rails_helper'

    ActiveRecord::Base.connection.disconnect!
  end

  conf.after_fork do |test_env_number|
    ##
    # uncomment if you're using SimpleCov and have started it in `rails_helper` as suggested here:
    # @see https://github.com/simplecov-ruby/simplecov/tree/main?tab=readme-ov-file#use-it-with-any-framework
    # SimpleCov.at_fork.call(test_env_number)

    config = ActiveRecord::Base.connection_db_config.configuration_hash

    ActiveRecord::Base.establish_connection(
      config.merge(
        database: config.fetch(:database) + test_env_number.to_s
      )
    )
  end
end

Now when I run bundle exec flatware rspec -r ./spec/flatware_helper My app only boots once, rather than once per core.

SimpleCov

If you're using SimpleCov, follow their directions to install. When you have it working as desired for serial runs, add SimpleCov.at_fork.call(test_env_number) to flatware's after_fork hook. You should now get the same coverage stats from parallel and serial runs.

Segmentation faults in the PG gem

If you get a segmentation fault on start you may need to add ENV["PGGSSENCMODE"] = "disable" to the top of your flatware helper.

Design Goals

Maintainable

• Fully test at an integration level. Don't be afraid to change the code. If you break it you'll know.
• Couple as loosely as possible, and only to the most stable/public bits of Cucumber and RSpec.

Minimal

• Projects define their own preparation scripts
• Only distribute to local cores (for now)

Robust

• Depend on a dedicated messaging library
• Be accountable for completed work; provide progress report regardless of completing the suite.

Tinkering

Flatware integration tests use aruba. In order to get a demo cucumber project you can add the @no-clobber tag to features/flatware.feature and run the test with cucumber features/flatware.feature. Now you should have a ./tmp/aruba directory. CD there and flatware will be in your path so you can tinker away.

How it works

Flatware relies on a message passing system to enable concurrency. The main process forks a worker for each cpu in the computer. These workers are each given a chunk of the tests to run. The workers report back to the main process about their progress. The main process prints those progress messages. When the last worker is finished the main process prints the results.

Resources

Contributing to Flatware

Do whatever you want. I'd love to help make sure Flatware meets your needs.

About

Flatware is supported by the team at Hashrocket, a multidisciplinary design & development consultancy. If you'd like to work with us or join our team, don't hesitate to get in touch.

TODO:

possible simplecov fixes

1. seems like we won't get the same results as serial rspec runs unless we start simplecov after fork. And if we do that, I think a process needs to claim to be the last one for simplecov to run the merge.