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module ActionCable::TestHelper

Provides helper methods for testing Action Cable broadcasting

Public instance methods

assert_broadcast_on(stream, data, &block)

Asserts that the specified message has been sent to the stream.

def test_assert_transmitted_message
  ActionCable.server.broadcast 'messages', text: 'hello'
  assert_broadcast_on('messages', text: 'hello')
end

If a block is passed, that block should cause a message with the specified data to be sent.

def test_assert_broadcast_on_again
  assert_broadcast_on('messages', text: 'hello') do
    ActionCable.server.broadcast 'messages', text: 'hello'
  end
end
Source code GitHub 
# File actioncable/lib/action_cable/test_helper.rb, line 116
def assert_broadcast_on(stream, data, &block)
  # Encode to JSON and back–we want to use this value to compare with decoded
  # JSON. Comparing JSON strings doesn't work due to the order if the keys.
  serialized_msg =
    ActiveSupport::JSON.decode(ActiveSupport::JSON.encode(data))

  new_messages = broadcasts(stream)
  if block_given?
    new_messages = new_broadcasts_from(new_messages, stream, "assert_broadcast_on", &block)
  end

  message = new_messages.find { |msg| ActiveSupport::JSON.decode(msg) == serialized_msg }

  error_message = "No messages sent with #{data} to #{stream}"

  if new_messages.any?
    error_message = new_messages.inject("#{error_message}\nMessage(s) found:\n") do |error_message, new_message|
      error_message + "#{ActiveSupport::JSON.decode(new_message)}\n"
    end
  else
    error_message = "#{error_message}\nNo message found for #{stream}"
  end

  assert message, error_message
end

assert_broadcasts(stream, number, &block)

Asserts that the number of broadcasted messages to the stream matches the given number.

def test_broadcasts
  assert_broadcasts 'messages', 0
  ActionCable.server.broadcast 'messages', { text: 'hello' }
  assert_broadcasts 'messages', 1
  ActionCable.server.broadcast 'messages', { text: 'world' }
  assert_broadcasts 'messages', 2
end

If a block is passed, that block should cause the specified number of messages to be broadcasted.

def test_broadcasts_again
  assert_broadcasts('messages', 1) do
    ActionCable.server.broadcast 'messages', { text: 'hello' }
  end

  assert_broadcasts('messages', 2) do
    ActionCable.server.broadcast 'messages', { text: 'hi' }
    ActionCable.server.broadcast 'messages', { text: 'how are you?' }
  end
end
Source code GitHub 
# File actioncable/lib/action_cable/test_helper.rb, line 48
def assert_broadcasts(stream, number, &block)
  if block_given?
    new_messages = new_broadcasts_from(broadcasts(stream), stream, "assert_broadcasts", &block)

    actual_count = new_messages.size
    assert_equal number, actual_count, "#{number} broadcasts to #{stream} expected, but #{actual_count} were sent"
  else
    actual_count = broadcasts(stream).size
    assert_equal number, actual_count, "#{number} broadcasts to #{stream} expected, but #{actual_count} were sent"
  end
end

assert_no_broadcasts(stream, &block)

Asserts that no messages have been sent to the stream.

def test_no_broadcasts
  assert_no_broadcasts 'messages'
  ActionCable.server.broadcast 'messages', { text: 'hi' }
  assert_broadcasts 'messages', 1
end

If a block is passed, that block should not cause any message to be sent.

def test_broadcasts_again
  assert_no_broadcasts 'messages' do
    # No job messages should be sent from this block
  end
end

Note: This assertion is simply a shortcut for:

assert_broadcasts 'messages', 0, &block
Source code GitHub 
# File actioncable/lib/action_cable/test_helper.rb, line 80
def assert_no_broadcasts(stream, &block)
  assert_broadcasts stream, 0, &block
end

capture_broadcasts(stream, &block)

Returns the messages that are broadcasted in the block.

def test_broadcasts
  messages = capture_broadcasts('messages') do
    ActionCable.server.broadcast 'messages', { text: 'hi' }
    ActionCable.server.broadcast 'messages', { text: 'how are you?' }
  end
  assert_equal 2, messages.length
  assert_equal({ text: 'hi' }, messages.first)
  assert_equal({ text: 'how are you?' }, messages.last)
end
Source code GitHub 
# File actioncable/lib/action_cable/test_helper.rb, line 96
def capture_broadcasts(stream, &block)
  new_broadcasts_from(broadcasts(stream), stream, "capture_broadcasts", &block).map { |m| ActiveSupport::JSON.decode(m) }
end

Definition files