have_stream_from matcher

The have_stream_from matcher is used to check if a channel has been subscribed to a given stream specified as a String. If you use stream_for in you channel to subscribe to a model, use have_stream_for matcher instead.

The have_no_streams matcher is used to check if a channel hasn't been subscribed to any stream.

It is available only in channel specs.

Background

Given action cable testing is available

And a file named "app/channels/chat_channel.rb" with:

class ChatChannel < ApplicationCable::Channel
  def subscribed
    reject unless params[:room_id].present?

    stream_from "chat_#{params[:room_id]}"
  end

  def leave
    stop_all_streams
  end
end

Subscribing with params and checking streams

Given a file named "spec/channels/chat_channel_spec.rb" with:

require "rails_helper"

RSpec.describe ChatChannel, type: :channel do
  it "successfully subscribes" do
    subscribe room_id: 42

    expect(subscription).to be_confirmed
    expect(subscription).to have_stream_from("chat_42")
  end
end

When I run rspec spec/channels/chat_channel_spec.rb

Then the example should pass.

Stopping all streams

Given a file named "spec/channels/chat_channel_spec.rb" with:

require "rails_helper"

RSpec.describe ChatChannel, type: :channel do
  it "successfully subscribes" do
    subscribe(room_id: 42)

    expect(subscription).to have_stream_from("chat_42")

    perform :leave
    expect(subscription).not_to have_streams
  end
end

When I run rspec spec/channels/chat_channel_spec.rb

Then the example should pass.

Subscribing and checking streams for models

Given a file named "app/channels/notifications_channel.rb" with:

class NotificationsChannel < ApplicationCable::Channel
  def subscribed
    stream_for current_user
  end
end

And a file named "app/channels/application_cable/connection.rb" with:

class ApplicationCable::Connection < ActionCable::Connection::Base
  identified_by :current_user
end

And a file named "app/models/user.rb" with:

class User < Struct.new(:name)
  def to_gid_param
    name
  end
end

And a file named "spec/channels/user_channel_spec.rb" with:

require "rails_helper"
RSpec.describe NotificationsChannel, type: :channel do
  it "successfully subscribes to user's stream" do
    stub_connection current_user: User.new(42)
    subscribe
    expect(subscription).to be_confirmed
    expect(subscription).to have_stream_for(User.new(42))
  end
end

When I run rspec spec/channels/user_channel_spec.rb

Then the example should pass.