Rspec + Factory girl (without rails!)

I am using Rspec with selenium-webdriver gem to test a web app. And I wanted to unclude factories in my tests to emulate users and not to create a user manually each time. So, I made gem install factory_girl, added required lined in my spec_helper, created a factory and included some lines in my spec file. And when running the test I get an error Failure/Error: FactoryGirl.build(:user) NameError: uninitialized constant User

Here is my spec_helper.rb

RSpec.configure do |config|
  config.include FactoryGirl::Syntax::Methods
  config.expect_with :rspec do |expectations|
  expectations.include_chain_clauses_in_custom_matcher_descriptions = true
end

My factories.rb file:

 FactoryGirl.define do
  factory :user do
    name "testuser"
    password "freestyle"
    inventory true
  end
end

And my test_spec file:

require "json"
require "selenium-webdriver"
require "rspec"
require "factory_girl"
FactoryGirl.find_definitions
include RSpec::Expectations

describe "MallSpec" do

  before(:all) do
    FactoryGirl.build(:user)
    @driver = Selenium::WebDriver.for :firefox
    @base_url = "http://localhost:9000/"
    @accept_next_alert = true
    @driver.manage.timeouts.implicit_wait = 30
    @driver.manage.window.resize_to(1301, 744)
    @verification_errors = []
end

My spec_file is in the root dir of the project. my factories.rb file is in /spec dir as well as the test_spec.rb itself. Can anyone help me with this issue or point what i am doing wrong?