parallel rake rspec

tests.rb

# frozen_string_literal: true

namespace :tests do
  desc "Create multiple test databases, load schema, seed data, and run RSpec tests in parallel"
  task :parallel, [:quantity] => :environment do |t, args|
    quantity = args[:quantity].to_i
    raise ArgumentError, "Please provide a valid quantity greater than 0." if quantity <= 0

    test_config = ActiveRecord::Base.configurations.configurations.find { |config| config.env_name == 'test' }
    raise "Test configuration not found." if test_config.nil?

    errors = []
    db_names = []

    quantity.times do |i|
      db_name = "test_#{SecureRandom.hex(4)}_#{i}"
      db_names << db_name
      config = test_config.configuration_hash.deep_dup
      config['database'] = db_name

      begin
        ActiveRecord::Base.establish_connection(config.merge('database' => 'postgres', 'schema_search_path' => 'public'))
        ActiveRecord::Base.connection.drop_database(config['database']) rescue nil
        ActiveRecord::Base.connection.create_database(config['database'])
        ActiveRecord::Base.establish_connection(config)

        system("DATABASE_URL=#{get_database_url(config, db_name)} rails db:schema:load --trace")
        system("rails db:seed")
      rescue ActiveRecord::StatementInvalid => e
        errors << e.message
      end
    end

    unless errors.empty?
      drop_databases(db_names)
      raise errors.join("\n")
    end

    test_files = Dir.glob("spec/**/*_spec.rb")
    files_per_db = (test_files.size / quantity.to_f).ceil

    Parallel.each_with_index(db_names, in_threads: quantity) do |db_name, index|
      config = test_config.configuration_hash.deep_dup
      config['database'] = db_name
      files_to_run = test_files.slice(index * files_per_db, files_per_db)

      next if files_to_run.nil? || files_to_run.empty?

      thread_config = config.dup
      thread_config['database'] = db_name
      database_url = get_database_url(thread_config, db_name)
      puts "Running tests for #{db_name}... in #{database_url}"
      ActiveRecord::Base.establish_connection(thread_config)
      system("DATABASE_URL=#{database_url} rspec #{files_to_run.join(' ')} --fail-fast --format documentation")
    end

    drop_databases(db_names)
  end

  private

  def get_database_url(config, db_name = nil)
    "#{config[:adapter]}://#{config[:username]}:#{config[:password]}@#{config[:host]}/#{db_name || config[:database]}"
  end

  def drop_databases(db_names)
    test_config = ActiveRecord::Base.configurations.configurations.find { |config| config.env_name == 'test' }

    db_names.each do |db_name|
      ActiveRecord::Base.establish_connection(test_config.configuration_hash.merge('database' => db_name))
      ActiveRecord::Base.connection.drop_database(db_name) rescue nil
    end
  end
end