# module ActiveSupport::LogSubscriber::TestHelper

Provides some helpers to deal with testing log subscribers by setting up notifications. Take for instance Active Record subscriber tests:

    class SyncLogSubscriberTest < ActiveSupport::TestCase
      include ActiveSupport::LogSubscriber::TestHelper

      def setup
        ActiveRecord::LogSubscriber.attach_to(:active_record)
      end

      def test_basic_query_logging
        Developer.all
        wait
        assert_equal 1, @logger.logged(:debug).size
        assert_match(%rDeveloper Load/, @logger.logged(:debug).last)
        assert_match(%rSELECT \* FROM "developers"/, @logger.logged(:debug).last)
      end
    end

All you need to do is to ensure that your log subscriber is added to Rails::Subscriber, as in the second line of the code above. The test helpers are responsible for setting up the queue, subscriptions and turning colors in logs off.

The messages are available in the @logger instance, which is a logger with limited powers (it actually does not send anything to your output), and you can collect them doing @logger.logged(level), where level is the level used in logging, like info, debug, warn and so on.

### Public Instance Methods

set_logger(logger) click to toggle source

Overwrite if you use another logger in your log subscriber:

    def logger
      ActiveRecord::Base.logger = @logger
    end

    # File lib/active_support/log_subscriber/test_helper.rb, line 96
    def set_logger(logger)
      ActiveSupport::LogSubscriber.logger = logger
    end

setup() click to toggle source

    # File lib/active_support/log_subscriber/test_helper.rb, line 36
    def setup
      @logger   = MockLogger.new
      @notifier = ActiveSupport::Notifications::Fanout.new

      ActiveSupport::LogSubscriber.colorize_logging = false

      @old_notifier = ActiveSupport::Notifications.notifier
      set_logger(@logger)
      ActiveSupport::Notifications.notifier = @notifier
    end

teardown() click to toggle source

    # File lib/active_support/log_subscriber/test_helper.rb, line 47
    def teardown
      set_logger(nil)
      ActiveSupport::Notifications.notifier = @old_notifier
    end

wait() click to toggle source

Wait notifications to be published.

    # File lib/active_support/log_subscriber/test_helper.rb, line 86
    def wait
      @notifier.wait
    end