Introduce Turbo::Broadcastable::TestHelper (#466)

README.md

@@ -139,6 +139,7 @@ The [`Turbo::TestAssertions`](./lib/turbo/test_assertions.rb) concern provides T
 
 The [`Turbo::TestAssertions::IntegrationTestAssertions`](./lib/turbo/test_assertions/integration_test_assertions.rb) are built on top of `Turbo::TestAssertions`, and add support for passing a `status:` keyword. They are automatically included in [`ActionDispatch::IntegrationTest`](https://edgeguides.rubyonrails.org/testing.html#integration-testing).
 
+The [`Turbo::Broadcastable::TestHelper`](./lib/turbo/broadcastable/test_helper.rb) concern provides Action Cable-aware test helpers that assert that `<turbo-stream>` elements were or were not broadcast over Action Cable. They are not automatically included. To use them in your tests, make sure to `include Turbo::Broadcastable::TestHelper`.
 
 ## Development
 

lib/turbo/broadcastable/test_helper.rb

@@ -0,0 +1,172 @@
+module Turbo
+  module Broadcastable
+    module TestHelper
+      extend ActiveSupport::Concern
+
+      included do
+        include ActionCable::TestHelper
+
+        include Turbo::Streams::StreamName
+      end
+
+      # Asserts that `<turbo-stream>` elements were broadcast over Action Cable
+      #
+      # === Arguments
+      #
+      # * <tt>stream_name_or_object</tt> the objects used to generate the
+      #   channel Action Cable name, or the name itself
+      # * <tt>&block</tt> optional block executed before the
+      #   assertion
+      #
+      # === Options
+      #
+      # * <tt>count:</tt> the number of `<turbo-stream>` elements that are
+      # expected to be broadcast
+      #
+      # Asserts `<turbo-stream>` elements were broadcast:
+      #
+      #     message = Message.find(1)
+      #     message.broadcast_replace_to "messages"
+      #
+      #     assert_turbo_stream_broadcasts "messages"
+      #
+      # Asserts that two `<turbo-stream>` elements were broadcast:
+      #
+      #     message = Message.find(1)
+      #     message.broadcast_replace_to "messages"
+      #     message.broadcast_remove_to "messages"
+      #
+      #     assert_turbo_stream_broadcasts "messages", count: 2
+      #
+      # You can pass a block to run before the assertion:
+      #
+      #     message = Message.find(1)
+      #
+      #     assert_turbo_stream_broadcasts "messages" do
+      #       message.broadcast_append_to "messages"
+      #     end
+      #
+      # In addition to a String, the helper also accepts an Object or Array to
+      # determine the name of the channel the elements are broadcast to:
+      #
+      #     message = Message.find(1)
+      #
+      #     assert_turbo_stream_broadcasts message do
+      #       message.broadcast_replace
+      #     end
+      #
+      def assert_turbo_stream_broadcasts(stream_name_or_object, count: nil, &block)
+        payloads = capture_turbo_stream_broadcasts(stream_name_or_object, &block)
+        stream_name = stream_name_from(stream_name_or_object)
+
+        if count.nil?
+          assert_not_empty payloads, "Expected at least one broadcast on #{stream_name.inspect}, but there were none"
+        else
+          broadcasts = "Turbo Stream broadcast".pluralize(count)
+
+          assert count == payloads.count, "Expected #{count} #{broadcasts} on #{stream_name.inspect}, but there were none"
+        end
+      end
+
+      # Asserts that no `<turbo-stream>` elements were broadcast over Action Cable
+      #
+      # === Arguments
+      #
+      # * <tt>stream_name_or_object</tt> the objects used to generate the
+      #   channel Action Cable name, or the name itself
+      # * <tt>&block</tt> optional block executed before the
+      #   assertion
+      #
+      # Asserts that no `<turbo-stream>` elements were broadcast:
+      #
+      #     message = Message.find(1)
+      #     message.broadcast_replace_to "messages"
+      #
+      #     assert_no_turbo_stream_broadcasts "messages" # fails with MiniTest::Assertion error
+      #
+      # You can pass a block to run before the assertion:
+      #
+      #     message = Message.find(1)
+      #
+      #     assert_no_turbo_stream_broadcasts "messages" do
+      #       # do something other than broadcast to "messages"
+      #     end
+      #
+      # In addition to a String, the helper also accepts an Object or Array to
+      # determine the name of the channel the elements are broadcast to:
+      #
+      #     message = Message.find(1)
+      #
+      #     assert_no_turbo_stream_broadcasts message do
+      #       # do something other than broadcast to "message_1"
+      #     end
+      #
+      def assert_no_turbo_stream_broadcasts(stream_name_or_object, &block)
+        block&.call
+
+        stream_name = stream_name_from(stream_name_or_object)
+
+        payloads = broadcasts(stream_name)
+
+        assert payloads.empty?, "Expected no broadcasts on #{stream_name.inspect}, but there were #{payloads.count}"
+      end
+
+      # Captures any `<turbo-stream>` elements that were broadcast over Action Cable
+      #
+      # === Arguments
+      #
+      # * <tt>stream_name_or_object</tt> the objects used to generate the
+      #   channel Action Cable name, or the name itself
+      # * <tt>&block</tt> optional block to capture broadcasts during execution
+      #
+      # Returns any `<turbo-stream>` elements that have been broadcast as an
+      # Array of <tt>Nokogiri::XML::Element</tt> instances
+      #
+      #     message = Message.find(1)
+      #     message.broadcast_append_to "messages"
+      #     message.broadcast_prepend_to "messages"
+      #
+      #     turbo_streams = capture_turbo_stream_broadcasts "messages"
+      #
+      #     assert_equal "append", turbo_streams.first["action"]
+      #     assert_equal "prepend", turbo_streams.second["action"]
+      #
+      # You can pass a block to limit the scope of the broadcasts being captured:
+      #
+      #     message = Message.find(1)
+      #
+      #     turbo_streams = capture_turbo_stream_broadcasts "messages" do
+      #       message.broadcast_append_to "messages"
+      #     end
+      #
+      #     assert_equal "append", turbo_streams.first["action"]
+      #
+      # In addition to a String, the helper also accepts an Object or Array to
+      # determine the name of the channel the elements are broadcast to:
+      #
+      #     message = Message.find(1)
+      #
+      #     replace, remove = capture_turbo_stream_broadcasts message do
+      #       message.broadcast_replace
+      #       message.broadcast_remove
+      #     end
+      #
+      #     assert_equal "replace", replace["action"]
+      #     assert_equal "replace", remove["action"]
+      #
+      def capture_turbo_stream_broadcasts(stream_name_or_object, &block)
+        block&.call
+
+        stream_name = stream_name_from(stream_name_or_object)
+        payloads = broadcasts(stream_name)
+
+        payloads.flat_map do |payload|
+          html = ActiveSupport::JSON.decode(payload)
+          document = Nokogiri::HTML5.parse(html)
+
+          document.at("body").element_children
+        end
+      end
+    end
+  end
+end

lib/turbo/engine.rb

@@ -75,6 +75,7 @@ class Engine < Rails::Engine
     initializer "turbo.test_assertions" do
       ActiveSupport.on_load(:active_support_test_case) do
         require "turbo/test_assertions"
+        require "turbo/broadcastable/test_helper"
 
         include Turbo::TestAssertions
       end