Posts tagged with "rails"

One of the most significant improvements in Rails 8 is the enhanced parallel testing system that now comes enabled by default. This feature dramatically reduces test suite execution time with minimal configuration.

What Changed in Rails 8

In previous Rails versions, you had to explicitly opt into parallel testing by adding configuration to your test environment. Rails 8 flips this approach - parallel testing is now enabled out of the box, automatically detecting your system's CPU count and utilizing those resources efficiently.

How to Get the Most Out of It

Here's how to leverage this feature effectively:

# config/environments/test.rb
Rails.application.configure do
  # The default is now true, but you can specify the number of workers
  config.parallel_testing.workers = :number_of_processors # or set specific number
  
  # You can also configure specific worker counts for different test types
  config.parallel_testing.workers = {
    models: 4,
    controllers: 3,
    system: 2
  }
end

Managing Database Setup

With parallel testing, each worker needs its own database. Rails 8 automatically handles this with a new task:

bin/rails parallel:setup

This creates numbered databases for each worker (like myapp_test-1, myapp_test-2).

Dealing with Shared Resources

When tests run in parallel, be careful with shared resources. Rails 8 includes helpers to manage this:

class SomeTest < ActiveSupport::TestCase
  parallelize_with :processes do |worker|
    # Code that runs once per worker
    Setup.prepare_shared_resource_for_worker(worker)
  end
  
  test "something that uses isolated resources" do
    # This test can run in parallel
  end
end

When to Turn It Off

Some tests may not work well in parallel. For specific test files:

class ComplexSystemTest < ApplicationSystemTestCase
  # Disable parallelization for just this test class
  self.use_parallel = false
  
  test "a complex flow that shouldn't run in parallel" do
    # Test code here
  end
end

Enjoy the significantly faster test execution times with Rails 8's parallel testing defaults!