Ruby on Rails cannot load such file -- selenium-webdriver Error

I am testing running selenium webdriver with phantomjs from Ruby on Rails. I am testing locally on my computer.

The following code runs fine within my test Ruby script when I run "ruby test.rb"

  def google_title
    require 'selenium-webdriver'
    driver = Selenium::WebDriver.for :phantomjs
    driver.navigate.to "https://www.google.com"
    page_title = driver.title
    puts page_title
  end

  google_title

I have pretty much the same code in my application_controller.rb file:

  def google_title
    require 'selenium-webdriver'
    driver = Selenium::WebDriver.for :phantomjs
    driver.navigate.to "https://www.google.com"
    page_title = driver.title
    render text: page_title
  end

But when I run my app I get a "cannot load such file -- selenium-webdriver" error.

I have added this to my Gemfile and ran bundle install but get the same error.

gem 'selenium-webdriver', '~> 2.45'

When I run gem list --local it shows selenium is installed.

Any help would be appreciated.

Update:

I ran almost exactly the same code as above but with watir-webdriver and got the same results. The Ruby script ran fine by it's self but gave a "cannot load such file" error for watir-webdriver when I tried to run it from Rails.

I ran another test with nokogiri and it worked fine. Both by it's self and in Rails.

Update2:

It appears to be something I am doing and not my test environment. I just ran the same code on an online IDE and got the same type of error:

Update3:

Here is the full content of the application_controller.rb file when I run the test with watir-webdriver and headless. I get the same results. Maybe I am setting something wrong here?

class ApplicationController < ActionController::Base
  def google_title
    require 'watir-webdriver'
    require 'headless'
    headless = Headless.new
    headless.start
    b = Watir::Browser.start 'www.google.com'
    page_title = b.title
    b.close
    headless.destroy
    render text: page_title
  end
end