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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
    super
    ActiveRecord::LogSubscriber.attach_to(:active_record)
  end

  def test_basic_query_logging
    Developer.all.to_a
    wait
    assert_equal 1, @logger.logged(:debug).size
    assert_match(/Developer Load/, @logger.logged(:debug).last)
    assert_match(/SELECT \* 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.

Namespace
Methods
S
W
Instance Public methods
set_logger(logger)

Overwrite if you use another logger in your log subscriber.

def logger
  ActiveRecord::Base.logger = @logger
end
# File activesupport/lib/active_support/log_subscriber/test_helper.rb, line 100
def set_logger(logger)
  ActiveSupport::LogSubscriber.logger = logger
end
wait()

Wait notifications to be published.

# File activesupport/lib/active_support/log_subscriber/test_helper.rb, line 91
def wait
  @notifier.wait
end