Add Action Cable test case and test helper

2 files changed, 143 insertions, 0 deletions

diff --git a/actioncable/lib/action_cable/test_case.rb b/actioncable/lib/action_cable/test_case.rb
new file mode 100644
index 0000000000..d153259bf6
--- /dev/null
+++ b/actioncable/lib/action_cable/test_case.rb
@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+require "active_support/test_case"
+
+module ActionCable
+  class TestCase < ActiveSupport::TestCase
+    include ActionCable::TestHelper
+
+    ActiveSupport.run_load_hooks(:action_cable_test_case, self)
+  end
+end
diff --git a/actioncable/lib/action_cable/test_helper.rb b/actioncable/lib/action_cable/test_helper.rb
new file mode 100644
index 0000000000..dbd5ec3b16
--- /dev/null
+++ b/actioncable/lib/action_cable/test_helper.rb
@@ -0,0 +1,132 @@
+# frozen_string_literal: true
+
+module ActionCable
+  # Provides helper methods for testing Action Cable broadcasting
+  module TestHelper
+    def before_setup # :nodoc:
+      server = ActionCable.server
+      test_adapter = ActionCable::SubscriptionAdapter::Test.new(server)
+
+      @old_pubsub_adapter = server.pubsub
+
+      server.instance_variable_set(:@pubsub, test_adapter)
+      super
+    end
+
+    def after_teardown # :nodoc:
+      super
+      ActionCable.server.instance_variable_set(:@pubsub, @old_pubsub_adapter)
+    end
+
+    # Asserts that the number of broadcasted messages to the stream matches the given number.
+    #
+    #   def test_broadcasts
+    #     assert_broadcasts 'messages', 0
+    #     ActionCable.server.broadcast 'messages', { text: 'hello' }
+    #     assert_broadcasts 'messages', 1
+    #     ActionCable.server.broadcast 'messages', { text: 'world' }
+    #     assert_broadcasts 'messages', 2
+    #   end
+    #
+    # If a block is passed, that block should cause the specified number of
+    # messages to be broadcasted.
+    #
+    #   def test_broadcasts_again
+    #     assert_broadcasts('messages', 1) do
+    #       ActionCable.server.broadcast 'messages', { text: 'hello' }
+    #     end
+    #
+    #     assert_broadcasts('messages', 2) do
+    #       ActionCable.server.broadcast 'messages', { text: 'hi' }
+    #       ActionCable.server.broadcast 'messages', { text: 'how are you?' }
+    #     end
+    #   end
+    #
+    def assert_broadcasts(stream, number)
+      if block_given?
+        original_count = broadcasts_size(stream)
+        yield
+        new_count = broadcasts_size(stream)
+        assert_equal number, new_count - original_count, "#{number} broadcasts to #{stream} expected, but #{new_count - original_count} were sent"
+      else
+        actual_count = broadcasts_size(stream)
+        assert_equal number, actual_count, "#{number} broadcasts to #{stream} expected, but #{actual_count} were sent"
+      end
+    end
+
+    # Asserts that no messages have been sent to the stream.
+    #
+    #   def test_no_broadcasts
+    #     assert_no_broadcasts 'messages'
+    #     ActionCable.server.broadcast 'messages', { text: 'hi' }
+    #     assert_broadcasts 'messages', 1
+    #   end
+    #
+    # If a block is passed, that block should not cause any message to be sent.
+    #
+    #   def test_broadcasts_again
+    #     assert_no_broadcasts 'messages' do
+    #       # No job messages should be sent from this block
+    #     end
+    #   end
+    #
+    # Note: This assertion is simply a shortcut for:
+    #
+    #   assert_broadcasts 'messages', 0, &block
+    #
+    def assert_no_broadcasts(stream, &block)
+      assert_broadcasts stream, 0, &block
+    end
+
+    # Asserts that the specified message has been sent to the stream.
+    #
+    #   def test_assert_transmited_message
+    #     ActionCable.server.broadcast 'messages', text: 'hello'
+    #     assert_broadcast_on('messages', text: 'hello')
+    #   end
+    #
+    # If a block is passed, that block should cause a message with the specified data to be sent.
+    #
+    #   def test_assert_broadcast_on_again
+    #     assert_broadcast_on('messages', text: 'hello') do
+    #       ActionCable.server.broadcast 'messages', text: 'hello'
+    #     end
+    #   end
+    #
+    def assert_broadcast_on(stream, data)
+      # Encode to JSON and back–we want to use this value to compare
+      # with decoded JSON.
+      # Comparing JSON strings doesn't work due to the order if the keys.
+      serialized_msg =
+        ActiveSupport::JSON.decode(ActiveSupport::JSON.encode(data))
+
+      new_messages = broadcasts(stream)
+      if block_given?
+        old_messages = new_messages
+        clear_messages(stream)
+
+        yield
+        new_messages = broadcasts(stream)
+        clear_messages(stream)
+
+        # Restore all sent messages
+        (old_messages + new_messages).each { |m| pubsub_adapter.broadcast(stream, m) }
+      end
+
+      message = new_messages.find { |msg| ActiveSupport::JSON.decode(msg) == serialized_msg }
+
+      assert message, "No messages sent with #{data} to #{stream}"
+    end
+
+    def pubsub_adapter # :nodoc:
+      ActionCable.server.pubsub
+    end
+
+    delegate :broadcasts, :clear_messages, to: :pubsub_adapter
+
+    private
+      def broadcasts_size(channel) # :nodoc:
+        broadcasts(channel).size
+      end
+  end
+end