Testing Action Cable subscriptions in Rails
Rails provides us great a great live features in terms of Action Cable, but have you already wrote tests for your subscriptions?
Stream assertions
Let's say we have a following channel implementation that subscribes a user to a chat room:
# app/channels/chat_channel.rb
class ChatChannel < ApplicationCable::Channel
def subscribed
if @room = find_room
stream_for @room
# or
stream_from "chat_#{params[:room_id]}"
else
reject
end
end
private
def find_room
Room.find_by(id: params[:room_id])
end
end
Then we can test this subscription implementation by writing tests subclassing ActionCable::Channel::TestCase like this:
require "test_helper"
class ChatChannelTest < ActionCable::Channel::TestCase
setup do
stub_connection(current_user: users(:joe))
@room = rooms(:introductions)
end
test "user can join a chat room" do
subscribe room_id: @room.id
assert subscription.confirmed?
assert_has_stream_for @room
# Or
assert_has_stream "chat_1"
end
test "user cannot join a non existing room" do
subscribe room_id: -1
assert subscription.rejected?
assert_no_stream
end
end
The stub_connection helper creates an Action Cable connection and subscribe subscribes to the ChatChannel. To test the subscription is successful, we can assert subscription.confirmed or subscription.rejected. To test the subscription subscribes to a specific stream, we can use assert_has_stream_for, assert_has_stream or assert_no_stream.
