Sinatra with activerecord transaction warnning.

20150110033835_create_student.rb

class CreateStudent < ActiveRecord::Migration
  def change
    create_table :users do |t|
      t.string  :name
      t.integer :age
    end
  end
end

configure.ru

require "./myApp"
run MyApp.new

database.rb

require "sinatra/activerecord"
set :database, {
  :adapter   => 'mysql2',
  :encoding  => 'utf8mb4',
  :reconnect => true,
  :database  => 'test_development',
  :pool      => 5,
  :username  => 'root',
  :password  => '123123',
  :host      => 'localhost',
  :socket    => '/tmp/mysql.sock',
}

FileStructure

Myapp
---------------------
Gemfile
Rakefile
config.ru
db
  ----migrate 
  --------20150110033835_create_student.rb
  ----schema.rb
myApp.rb
Gemfile.lock 
app         
   ----controllers
   ----models   
      ----student.rb
   ----views
database.rb 
rspec
----myApp_spec.rb  
----spec_helper.rb

Gemfile

source 'https://rubygems.org'
 
gem 'rake'
gem 'sinatra'
gem 'activerecord', '4.2', :require => 'active_record'
gem 'mysql2'

MyApp.rb

ROOT = File.expand_path('./..', __FILE__) unless defined?(ROOT)

require 'sinatra'
require 'active_record'

require './database'
 
 ['./app/controllers', './app/models', './app/views'].each do |path|
  Dir.glob("#{ROOT}/#{path}/*.rb") do |filename|
    require filename
  end
end
class MyApp < Sinatra::Base
  get '/' do
    'Hello World!'
  end
end

myApp_spec.rb

require './spec_helper'

describe "Main API" do
  it "should respond to GET" do
    get '/'
    expect(response.status).to eq 200
  end
end

spec_helper.rb

require File.join(File.dirname(__FILE__), '..', 'myApp.rb')

require 'sinatra'
require 'rack/test'

set :environment, :test
set :run, false
set :raise_errors, true
set :logging, false

def app
  Sinatra::Application
end

RSpec.configure do |config|
  config.include Rack::Test::Methods
end

student.rb

#after_commit with case the issue
class Student < ActiveRecord::Base
  after_commit :print_hello
  
  def print_hello
    p "hello world"
  end
  
end