I’m trying to improve the tests for my ActionCable system but I’m having a hard time. In test, it seems like my stream_from("something") { ... } handlers aren’t actually called. I was trying to debug and I made a minimal test case in a new Rails 7.2.1 app.

First, I made an empty ActionCable channel:

# app/channels/test_channel.rb
class TestChannel < ApplicationCable::Channel
end

Then, I wrote a test just to see if I could make it work:

require "test_helper"

class TestChannelTest < ActionCable::Channel::TestCase
  test "it works at all" do
    subscribe

    assert subscription.confirmed?

    last_message = nil
    subscription.stream_from("something") do |message|
      last_message = message
    end

    ActionCable.server.broadcast("something", 100)

    assert_equal(100, last_message)
  end
end

But this test fails:

# Running:

F

Failure:
TestChannelTest#test_it_works_at_all [test/channels/test_channel_test.rb:14]:
Expected: 100
  Actual: nil

As far as I can tell, the stream_from block is never called at all.

What am I missing? How can I make this test pass?