ParallelRSpec

This gem lets you run your RSpec examples in parallel across your CPUs. Each worker gets its own database to avoid conflicts.

Installation

Add this to your application's Gemfile:

group :development, :test do
  gem 'parallel_rspec'
end

Or if you use Spring:

group :development, :test do
  gem 'spring-prspec'
end

And then execute:

$ bundle

This version of ParallelRSpec has been tested with RSpec 3.12.

Usage

By default, ParallelRSpec will use four workers. If you would like to use more, set an environment variable:

$ export WORKERS=8

ParallelRSpec runs each worker with its own copy of the test database to avoid locking and deadlocking problems. To create these and populate them with your schema, run:

$ bundle exec rake db:parallel:create db:parallel:prepare

ParallelRSpec will automatically make the database name for each worker based on the name you used for the test environment in config/database.yml. For example, if your normal test database is foo_test, worker 1 will keep using foo_test but worker 2's database will be foo_test2.

You're then ready to run specs in parallel:

$ bundle exec prspec spec/my_spec.rb spec/another_spec.rb

Or if you use Spring:

$ bundle exec spring prspec spec/my_spec.rb spec/another_spec.rb

You may like to make an alias:

$ alias prspec='bundle exec spring prspec'
$ prspec spec/my_spec.rb spec/another_spec.rb

When you change WORKERS, don't forget to restart Spring and re-run the create and populate steps above if necessary.

By default, there's a task called parallel_rspec which will run all specs. To make a custom rake task which uses parallel_rspec with different options, inherit from ParallelRSpec::RakeTask, for example:

  require 'parallel_rspec'

  ParallelRSpec::RakeTask.new(:prspec) do |t|
    ENV['WORKERS'] = '8'
    t.pattern = "spec/**/*_spec.rb"
    t.rspec_opts = "--tag parallel"
    # etc...
  end

If you'd like code to run after parallel_rspec has created each worker, you can specify a block to run:

  ParallelRSpec.configure do |config|
    config.after_fork do |worker_number|
      puts "I am worker #{worker_number}"
    end
  end

You might also want to detect whether your spec suite is running under ParallelRSpec or not:

  do_something unless ParallelRSpec.running?

Limitations

ParallelRSpec can't parallelize the specs in groups that use before(:context) or after(:context) (AKA before(:all) or after(:all)) hooks, since these may mean that there is state shared between examples.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/willbryant/parallel_rspec.

Thanks

Charles Horn (@hornc)
Roger Nesbitt (@mogest)
Erik Paasonen (@erikpaasonen)
Peter Retzlaff (@peret)

License

The gem is available as open source under the terms of the MIT License.