Create Rails::Subscriber::TestHelper and use it to make ActiveRecord subscriber tests run in both sync and async scenarios.

1 files changed, 106 insertions, 0 deletions

diff --git a/railties/lib/rails/subscriber/test_helper.rb b/railties/lib/rails/subscriber/test_helper.rb
new file mode 100644
index 0000000000..d8a8551a45
--- /dev/null
+++ b/railties/lib/rails/subscriber/test_helper.rb
@@ -0,0 +1,106 @@
+require 'rails'
+require 'rails/subscriber'
+
+module Rails
+  class Subscriber
+    # Provides some helpers to deal with testing subscribers by setting up
+    # notifications. Take for instance ActiveRecord subscriber tests:
+    #
+    #   module SubscriberTest
+    #     Rails::Subscriber.add(:active_record, ActiveRecord::Railties::Subscriber.new)
+    # 
+    #     def test_basic_query_logging
+    #       Developer.all
+    #       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
+    # 
+    #     class SyncSubscriberTest < ActiveSupport::TestCase
+    #       include Rails::Subscriber::SyncTestHelper
+    #       include SubscriberTest
+    #     end
+    # 
+    #     class AsyncSubscriberTest < ActiveSupport::TestCase
+    #       include Rails::Subscriber::AsyncTestHelper
+    #       include SubscriberTest
+    #     end
+    #   end
+    #
+    # All you need to do is to ensure that your subscriber is added to Rails::Subscriber,
+    # as in the second line of the code above. The test helpers is reponsible 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 do 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.
+    #
+    module TestHelper
+      def setup
+        Thread.abort_on_exception = true
+
+        @logger   = MockLogger.new
+        @notifier = ActiveSupport::Notifications::Notifier.new(queue)
+
+        Rails::Subscriber.colorize_logging = false
+        @notifier.subscribe { |*args| Rails::Subscriber.dispatch(args) }
+
+        set_logger(@logger)
+        ActiveSupport::Notifications.notifier = @notifier
+      end
+
+      def teardown
+        set_logger(nil)
+        ActiveSupport::Notifications.notifier = nil
+        Thread.abort_on_exception = false
+      end
+
+      class MockLogger
+        def initialize
+          @logged = Hash.new { |h,k| h[k] = [] }
+        end
+
+        def method_missing(level, message)
+          @logged[level] << message
+        end
+
+        def logged(level)
+          @logged[level].compact.map { |l| l.to_s.strip }
+        end
+      end
+
+      # Wait notifications to be published.
+      def wait
+        @notifier.wait
+      end
+
+      # Overwrite if you use another logger in your subscriber:
+      #
+      #   def logger
+      #     ActiveRecord::Base.logger = @logger
+      #   end
+      #
+      def set_logger(logger)
+        Rails.logger = logger
+      end
+    end
+    
+    module SyncTestHelper
+      include TestHelper
+
+      def queue
+        ActiveSupport::Notifications::Fanout.new(true)
+      end
+    end
+
+    module AsyncTestHelper
+      include TestHelper
+
+      def queue
+        ActiveSupport::Notifications::Fanout.new(false)
+      end
+    end
+  end
+end
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