You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: reads_controller_spec.rb
    path of file: ./repos/discourse/plugins/chat/spec/requests/chat/api
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

RSpec.describe Chat::Api::ReadsController do
  fab!(:current_user) { Fabricate(:user) }

  before do
    SiteSetting.chat_enabled = true
    SiteSetting.chat_allowed_groups = Group::AUTO_GROUPS[:everyone]
    sign_in(current_user)
  end

  describe "#read" do
    describe "marking a single message read" do
      fab!(:chat_channel)
      fab!(:other_user) { Fabricate(:user) }
      fab!(:message_1) { Fabricate(:chat_message, chat_channel: chat_channel, user: other_user) }
      fab!(:message_2) { Fabricate(:chat_message, chat
    
  def create_notification_and_mention_for(user, sender, msg)
    Notification
      .create!(
        notification_type: Notification.types[:chat_mention],
        user: user,
        high_priority: true,
        read: false,
        data: {
          message: "chat.mention_notification",
          chat_message_id: msg.id,
          chat_channel_id: msg.chat_channel_id,
          chat_channel_title: msg.chat_channel.title(user),
          chat_channel_slug: msg.chat_channel.slug,
          mentioned_by_username: sender.username,
        }.to_json,
      )
      .tap do |notification|
        Chat::UserMention.create!(user: user, chat_message: msg, notifications: [notification])
      end
  end