That would allow us to test broadcasting made with channel, e.g.:
```ruby
class ChatRelayJob < ApplicationJob
def perform_later(room, msg)
ChatChannel.broadcast_to room, message: msg
end
end
```
To test this functionality we need to know the underlying stream name
(to use `assert_broadcasts`), which relies on `channel_name`.
We had to use the following code:
```ruby
assert_broadcasts(ChatChannel.broadcasting_for([ChatChannel.channel_name, room]), 1) do
ChatRelayJob.perform_now
end
```
The problem with this approach is that we use _internal_ API (we shouldn't care about `channel_name` prefix
in our code).
With this commit we could re-write the test as following:
```ruby
assert_broadcasts(ChatChannel.broadcasting_for(room), 1) do
ChatRelayJob.perform_now
end
```
Remove all `include ActiveSupport::Testing::MethodCallAssertions`
in actioncable's tests since we can do it only in `ActionCable::TestCase`
in order to prevent code duplication.
We use the same approach for other modules of Rails.
We have defined `ActionCable::TestCase` in `actioncable/test/test_helper.rb`
that we can use in order to prevent code duplication and build common
interface for actioncable's test.
