1 files changed, 56 insertions, 0 deletions
diff --git a/activesupport/test/subscriber_test.rb b/activesupport/test/subscriber_test.rb
new file mode 100644
index 0000000000..6b012e43af
--- /dev/null
+++ b/activesupport/test/subscriber_test.rb
@@ -0,0 +1,56 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+require "active_support/subscriber"
+
+class TestSubscriber < ActiveSupport::Subscriber
+  attach_to :doodle
+
+  cattr_reader :events
+
+  def self.clear
+    @@events = []
+  end
+
+  def open_party(event)
+    events << event
+  end
+
+  private
+
+    def private_party(event)
+      events << event
+    end
+end
+
+# Monkey patch subscriber to test that only one subscriber per method is added.
+class TestSubscriber
+  remove_method :open_party
+  def open_party(event)
+    events << event
+  end
+end
+
+class SubscriberTest < ActiveSupport::TestCase
+  def setup
+    TestSubscriber.clear
+  end
+
+  def test_attaches_subscribers
+    ActiveSupport::Notifications.instrument("open_party.doodle")
+
+    assert_equal "open_party.doodle", TestSubscriber.events.first.name
+  end
+
+  def test_attaches_only_one_subscriber
+    ActiveSupport::Notifications.instrument("open_party.doodle")
+
+    assert_equal 1, TestSubscriber.events.size
+  end
+
+  def test_does_not_attach_private_methods
+    ActiveSupport::Notifications.instrument("private_party.doodle")
+
+    assert_equal [], TestSubscriber.events
+  end
+end