Such as setting when you write a test of parallel processing in ActiveRecord

database_clenaer.rb

# spec_helper.rb
RSpec.configure do |config|
  ...
  # テスト完了後一度だけ実行される
  config.after(:suite) do
    DatabaseCleaner.clean_with(:truncation)
  end
  
  # 各テスト実行前に実行される
  config.before(:each) do |spec|
    # multithread が trueのときは truncation
    if spec.metadata[:multithread]
      DatabaseCleaner.strategy = :truncation
    else
      DatabaseCleaner.strategy = :transaction
    end
    
    DatabaseCleaner.start
  end
  
  # 各テスト実行後に実行される
  config.after(:each) do
    DatabaseCleaner.clean
  end

  ...
end

test_spec.rb

 require 'spec_helper'
 
  describe Application do
    # マルチスレッドのテスト
    it 'multi thread doing', multithread: true do
      ...
    end
  end
  

transactional_fixtures.rb

# spec_helper.rb
RSpec.configure do |config|
  ...
  
  config.use_transactional_fixtures = false

  ...
end