Add assertions for stopped ActionCable streams

This adds two new assertion methods for ActionCable test cases:
`assert_not_has_stream` and `assert_not_has_stream_for`. These methods
can be used to assert that a stream has been stopped, e.g. via
`stop_stream` or `stop_stream_for`.

Author: SebastianPoell

actioncable/CHANGELOG.md

@@ -1,2 +1,13 @@
+*   Add two new assertion methods for ActionCable test cases: `assert_not_has_stream`
+    and `assert_not_has_stream_for`. These methods can be used to assert that a
+    stream has been stopped, e.g. via `stop_stream` or `stop_stream_for`. They complement
+    the already existing `assert_has_stream` and `assert_has_stream_for` methods.
+
+    ```ruby
+    assert_not_has_stream "messages"
+    assert_not_has_stream_for User.find(42)
+    ```
+
+    *Sebastian Pöll*
 
 Please check [7-1-stable](https://github.com/rails/rails/blob/7-1-stable/actioncable/CHANGELOG.md) for previous changes.

actioncable/lib/action_cable/channel/test_case.rb

@@ -312,6 +312,28 @@ def assert_has_stream_for(object)
           assert_has_stream(broadcasting_for(object))
         end
 
+        # Asserts that the specified stream has not been started.
+        #
+        #   def test_assert_not_started_stream
+        #     subscribe
+        #     assert_not_has_stream 'messages'
+        #   end
+        #
+        def assert_not_has_stream(stream)
+          assert subscription.streams.exclude?(stream), "Stream #{stream} has been started"
+        end
+
+        # Asserts that the specified stream for a model has not started.
+        #
+        #   def test_assert_not_started_stream_for
+        #     subscribe id: 41
+        #     assert_not_has_stream_for User.find(42)
+        #   end
+        #
+        def assert_not_has_stream_for(object)
+          assert_not_has_stream(broadcasting_for(object))
+        end
+
         private
           def check_subscribed!
             raise "Must be subscribed!" if subscription.nil? || subscription.rejected?

actioncable/test/channel/test_case_test.rb

@@ -107,6 +107,20 @@ def test_stream_with_params
     assert_has_stream "test_42"
   end
 
+  def test_not_stream_without_params
+    subscribe
+    unsubscribe
+
+    assert_not_has_stream "test_0"
+  end
+
+  def test_not_stream_with_params
+    subscribe id: 42
+    perform :unsubscribed, id: 42
+
+    assert_not_has_stream "test_42"
+  end
+
   def test_unsubscribe_from_stream
     subscribe
     unsubscribe
@@ -119,6 +133,10 @@ class StreamsForTestChannel < ActionCable::Channel::Base
   def subscribed
     stream_for User.new(params[:id])
   end
+
+  def unsubscribed
+    stop_stream_for User.new(params[:id])
+  end
 end
 
 class StreamsForTestChannelTest < ActionCable::Channel::TestCase
@@ -127,6 +145,13 @@ def test_stream_with_params
 
     assert_has_stream_for User.new(42)
   end
+
+  def test_not_stream_with_params
+    subscribe id: 42
+    perform :unsubscribed, id: 42
+
+    assert_not_has_stream_for User.new(42)
+  end
 end
 
 class NoStreamsTestChannel < ActionCable::Channel::Base