diff --git a/.gitignore b/.gitignore
index b0cd433..caa5d1e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,4 +6,5 @@ test/dummy/tmp/
 test/dummy/.sass-cache
 Gemfile.lock
 .idea/
-*.gem
\ No newline at end of file
+*.gem
+coverage/
\ No newline at end of file
diff --git a/.rubocop.yml b/.rubocop.yml
new file mode 100644
index 0000000..b3fa9d6
--- /dev/null
+++ b/.rubocop.yml
@@ -0,0 +1,56 @@
+require:
+ - rubocop-performance
+
+AllCops:
+  TargetRubyVersion: 2.3
+
+Layout/SpaceInsideHashLiteralBraces:
+  EnforcedStyle: no_space
+
+Metrics/BlockLength:
+  Max: 36
+  Exclude:
+    - spec/**/*.rb
+
+Metrics/BlockNesting:
+  Max: 2
+
+Layout/LineLength:
+  AllowURI: true
+  Enabled: false
+
+Metrics/MethodLength:
+  CountComments: false
+  Max: 10
+
+Metrics/ModuleLength:
+  Max: 100
+
+Metrics/ParameterLists:
+  Max: 5
+  CountKeywordArgs: true
+
+Style/CollectionMethods:
+  Enabled: true
+  PreferredMethods:
+    collect:  'map'
+    collect!: 'map!'
+    inject:   'reduce'
+    find:     'detect'
+    find_all: 'select'
+    delete:   'gsub'
+
+Style/Documentation:
+  Enabled: false
+
+Layout/DotPosition:
+  EnforcedStyle: trailing
+
+Layout/AccessModifierIndentation:
+  Enabled: false
+
+Style/TrailingCommaInArrayLiteral:
+  EnforcedStyleForMultiline: 'no_comma'
+
+Style/TrailingCommaInHashLiteral:
+  EnforcedStyleForMultiline: 'no_comma'
\ No newline at end of file
diff --git a/.travis.yml b/.travis.yml
index fd60548..5b18163 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,15 +2,13 @@ language: ruby
 sudo: false
 cache: bundler
 rvm:
-  - 2.5.5
-  - 2.6.3
+  - 2.5.7
+  - 2.6.5
 
 before_install:
-  - gem update --system
-  - gem install bundler
+  - gem update bundler
 
 env:
-  - 'TEST_RAILS_VERSION="~> 5.0.7"'
   - 'TEST_RAILS_VERSION="~> 5.1.6"'
   - 'TEST_RAILS_VERSION="~> 5.2.3"'
   - 'TEST_RAILS_VERSION="~> 6.0.0"'
\ No newline at end of file
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8fbc6fa..7161f1b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # Changelog
 
+## 4.0.1 (23-Dec-19)
+
+* Updated dependencies, tested against more recent Rubies and Rails
+* Updated Gemfile for Bundler 2
+* Added Rubocop and SimpleCov
+
 ## 4.0.0 (20-Aug-19)
 
 Updated:
diff --git a/Gemfile b/Gemfile
index 8ab4ecf..e193a12 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,7 +1,9 @@
-source "https://rubygems.org"
+# frozen_string_literal: true
+
+source 'https://rubygems.org'
 
 gemspec
 
 group :test do
-  gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]
-end
\ No newline at end of file
+  gem 'tzinfo-data', platforms: %i[mingw mswin x64_mingw jruby]
+end
diff --git a/Rakefile b/Rakefile
index 24fb892..16bdbc5 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 begin
   require 'bundler/setup'
 rescue LoadError
@@ -14,9 +16,6 @@ RDoc::Task.new(:rdoc) do |rdoc|
   rdoc.rdoc_files.include('lib/**/*.rb')
 end
 
-
-
-
 Bundler::GemHelper.install_tasks
 
 require 'rake/testtask'
@@ -28,5 +27,4 @@ Rake::TestTask.new(:test) do |t|
   t.verbose = false
 end
 
-
 task default: :test
diff --git a/angular_rails_csrf.gemspec b/angular_rails_csrf.gemspec
index e084f95..526b5f3 100644
--- a/angular_rails_csrf.gemspec
+++ b/angular_rails_csrf.gemspec
@@ -1,11 +1,13 @@
-$:.push File.expand_path("../lib", __FILE__)
+# frozen_string_literal: true
+
+$LOAD_PATH.push File.expand_path('lib', __dir__)
 
 # Maintain your gem's version:
-require "angular_rails_csrf/version"
+require 'angular_rails_csrf/version'
 
 # Describe your gem and declare its dependencies:
 Gem::Specification.new do |s|
-  s.name        = "angular_rails_csrf"
+  s.name        = 'angular_rails_csrf'
   s.version     = AngularRailsCsrf::VERSION
   s.authors     = ['James Sanders', 'Ilya Bodrov']
   s.email       = ['sanderjd@gmail.com', 'golosizpru@gmail.com']
@@ -19,13 +21,18 @@ Gem::Specification.new do |s|
 
   s.required_ruby_version = '>= 2.3.0'
 
-  s.add_development_dependency 'rake', '~> 12.0'
+  s.add_development_dependency 'rake', '~> 13.0'
   s.add_development_dependency 'test-unit', '~> 3.2'
   if ENV['TEST_RAILS_VERSION'].nil?
-    s.add_development_dependency 'rails', '6.0.0'
+    s.add_development_dependency 'rails', '6.0.2.1'
   else
     s.add_development_dependency 'rails', ENV['TEST_RAILS_VERSION'].to_s
   end
 
   s.add_runtime_dependency 'railties', '>= 3', '< 7'
+
+  s.add_development_dependency 'codecov',                   '~> 0.1'
+  s.add_development_dependency 'rubocop',                   '~> 0.60'
+  s.add_development_dependency 'rubocop-performance',       '~> 1.5'
+  s.add_development_dependency 'simplecov',                 '~> 0.16'
 end
diff --git a/lib/angular_rails_csrf.rb b/lib/angular_rails_csrf.rb
index 16a72cb..1a71727 100644
--- a/lib/angular_rails_csrf.rb
+++ b/lib/angular_rails_csrf.rb
@@ -1 +1,3 @@
+# frozen_string_literal: true
+
 require 'angular_rails_csrf/railtie'
diff --git a/lib/angular_rails_csrf/concern.rb b/lib/angular_rails_csrf/concern.rb
index 1dda9ec..4a35647 100644
--- a/lib/angular_rails_csrf/concern.rb
+++ b/lib/angular_rails_csrf/concern.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module AngularRailsCsrf
   module Concern
     extend ActiveSupport::Concern
@@ -7,12 +9,12 @@ module Concern
     end
 
     def set_xsrf_token_cookie
-      if protect_against_forgery? && !respond_to?(:__exclude_xsrf_token_cookie?)
-        config = Rails.application.config
-        domain = config.respond_to?(:angular_rails_csrf_domain) ? config.angular_rails_csrf_domain : nil
-        cookie_name = config.respond_to?(:angular_rails_csrf_cookie_name) ? config.angular_rails_csrf_cookie_name : 'XSRF-TOKEN'
-        cookies[cookie_name] = { value: form_authenticity_token, domain: domain }
-      end
+      return unless protect_against_forgery? && !respond_to?(:__exclude_xsrf_token_cookie?)
+
+      config = Rails.application.config
+      domain = config.respond_to?(:angular_rails_csrf_domain) ? config.angular_rails_csrf_domain : nil
+      cookie_name = config.respond_to?(:angular_rails_csrf_cookie_name) ? config.angular_rails_csrf_cookie_name : 'XSRF-TOKEN'
+      cookies[cookie_name] = {value: form_authenticity_token, domain: domain}
     end
 
     def verified_request?
@@ -25,7 +27,7 @@ def verified_request?
 
     module ClassMethods
       def exclude_xsrf_token_cookie
-        self.class_eval do
+        class_eval do
           def __exclude_xsrf_token_cookie?
             true
           end
diff --git a/lib/angular_rails_csrf/railtie.rb b/lib/angular_rails_csrf/railtie.rb
index bce0826..e36ea4b 100644
--- a/lib/angular_rails_csrf/railtie.rb
+++ b/lib/angular_rails_csrf/railtie.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'angular_rails_csrf/concern'
 
 module AngularRailsCsrf
diff --git a/lib/angular_rails_csrf/version.rb b/lib/angular_rails_csrf/version.rb
index 855862f..b1d230b 100644
--- a/lib/angular_rails_csrf/version.rb
+++ b/lib/angular_rails_csrf/version.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module AngularRailsCsrf
-  VERSION = '4.0.0'.freeze
+  VERSION = '4.0.1'
 end
diff --git a/test/angular_rails_csrf_exception_test.rb b/test/angular_rails_csrf_exception_test.rb
index e4f134b..b9ed51e 100644
--- a/test/angular_rails_csrf_exception_test.rb
+++ b/test/angular_rails_csrf_exception_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class AngularRailsCsrfExceptionTest < ActionController::TestCase
@@ -8,9 +10,9 @@ class AngularRailsCsrfExceptionTest < ActionController::TestCase
     @correct_token = @controller.send(:form_authenticity_token)
   end
 
-  test "a get does not set the XSRF-TOKEN cookie" do
+  test 'a get does not set the XSRF-TOKEN cookie' do
     get :index
     assert_not_equal @correct_token, cookies['XSRF-TOKEN']
     assert_response :success
   end
-end
\ No newline at end of file
+end
diff --git a/test/angular_rails_csrf_test.rb b/test/angular_rails_csrf_test.rb
index 9be12a0..e9e3a25 100644
--- a/test/angular_rails_csrf_test.rb
+++ b/test/angular_rails_csrf_test.rb
@@ -1,37 +1,41 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class AngularRailsCsrfTest < ActionController::TestCase
   tests ApplicationController
 
-  test "a get sets the XSRF-TOKEN cookie but does not require the X-XSRF-TOKEN header" do
+  test 'a get sets the XSRF-TOKEN cookie but does not require the X-XSRF-TOKEN header' do
     get :index
     assert_valid_cookie
     assert_response :success
   end
 
-  test "a post raises an error without the X-XSRF-TOKEN header set" do
+  test 'a post raises an error without the X-XSRF-TOKEN header set' do
     assert_raises ActionController::InvalidAuthenticityToken do
       post :create
     end
   end
 
-  test "a post raises an error with the X-XSRF-TOKEN header set to the wrong value" do
-    set_header_to 'garbage'
+  test 'a post raises an error with the X-XSRF-TOKEN header set to the wrong value' do
+    header_to 'garbage'
     assert_raises ActionController::InvalidAuthenticityToken do
       post :create
     end
   end
 
-  test "a post is accepted if X-XSRF-TOKEN is set properly" do
-    set_header_to @controller.send(:form_authenticity_token)
+  test 'a post is accepted if X-XSRF-TOKEN is set properly' do
+    header_to @controller.send(:form_authenticity_token)
     post :create
     assert_valid_cookie
     assert_response :success
   end
 
-  test "the domain is used if present" do
+  test 'the domain is used if present' do
     config = Rails.application.config
-    def config.angular_rails_csrf_domain; :all; end
+    def config.angular_rails_csrf_domain
+      :all
+    end
 
     get :index
     assert @response.headers['Set-Cookie'].include?('.test.host')
@@ -39,7 +43,7 @@ def config.angular_rails_csrf_domain; :all; end
     assert_response :success
   end
 
-  test "a custom name is used if present" do
+  test 'a custom name is used if present' do
     use_custom_cookie_name do
       get :index
       assert @response.headers['Set-Cookie'].include?('CUSTOM-COOKIE-NAME')
@@ -52,7 +56,7 @@ def config.angular_rails_csrf_domain; :all; end
 
   # Helpers
 
-  def set_header_to(value)
+  def header_to(value)
     @request.headers['X-XSRF-TOKEN'] = value
   end
 
@@ -66,9 +70,13 @@ def assert_valid_cookie(name = 'XSRF-TOKEN')
 
   def use_custom_cookie_name
     config = Rails.application.config
-    def config.angular_rails_csrf_cookie_name; 'CUSTOM-COOKIE-NAME'; end
+    def config.angular_rails_csrf_cookie_name
+      'CUSTOM-COOKIE-NAME'
+    end
     yield
   ensure
-    config.instance_eval('undef :angular_rails_csrf_cookie_name')
+    eval <<-RUBY, binding, __FILE__, __LINE__ + 1
+      config.instance_eval('undef :angular_rails_csrf_cookie_name')
+    RUBY
   end
 end
diff --git a/test/dummy/app/assets/config/manifest.js b/test/dummy/app/assets/config/manifest.js
new file mode 100644
index 0000000..88ee63b
--- /dev/null
+++ b/test/dummy/app/assets/config/manifest.js
@@ -0,0 +1,4 @@
+//= link_tree ../images
+//= link_tree ../fonts
+//= link_directory ../javascripts .js
+//= link_directory ../stylesheets .css
\ No newline at end of file
diff --git a/test/dummy/app/controllers/application_controller.rb b/test/dummy/app/controllers/application_controller.rb
index a40598c..0d102ed 100644
--- a/test/dummy/app/controllers/application_controller.rb
+++ b/test/dummy/app/controllers/application_controller.rb
@@ -1,6 +1,13 @@
+# frozen_string_literal: true
+
 class ApplicationController < ActionController::Base
   protect_from_forgery with: :exception
 
-  def index;  head :ok; end
-  def create; head :ok; end
+  def index
+    head :ok
+  end
+
+  def create
+    head :ok
+  end
 end
diff --git a/test/dummy/app/controllers/exclusions_controller.rb b/test/dummy/app/controllers/exclusions_controller.rb
index 04a1947..1143f92 100644
--- a/test/dummy/app/controllers/exclusions_controller.rb
+++ b/test/dummy/app/controllers/exclusions_controller.rb
@@ -1,5 +1,9 @@
+# frozen_string_literal: true
+
 class ExclusionsController < ApplicationController
   exclude_xsrf_token_cookie
 
-  def index;  head :ok; end
-end
\ No newline at end of file
+  def index
+    head :ok
+  end
+end
diff --git a/test/dummy/config.ru b/test/dummy/config.ru
index 5bc2a61..61c04e1 100644
--- a/test/dummy/config.ru
+++ b/test/dummy/config.ru
@@ -1,4 +1,6 @@
+# frozen_string_literal: true
+
 # This file is used by Rack-based servers to start the application.
 
-require ::File.expand_path('../config/environment',  __FILE__)
+require ::File.expand_path('../config/environment', __FILE__)
 run Rails.application
diff --git a/test/dummy/config/application.rb b/test/dummy/config/application.rb
index 17ee306..aa47bed 100644
--- a/test/dummy/config/application.rb
+++ b/test/dummy/config/application.rb
@@ -1,9 +1,11 @@
-require File.expand_path('../boot', __FILE__)
+# frozen_string_literal: true
 
-require "action_controller/railtie"
+require File.expand_path('boot', __dir__)
+
+require 'action_controller/railtie'
 
 Bundler.require(:default, Rails.env)
-require "angular_rails_csrf"
+require 'angular_rails_csrf'
 
 module Dummy
   class Application < Rails::Application
@@ -12,4 +14,3 @@ class Application < Rails::Application
     config.active_support.test_order = :random
   end
 end
-
diff --git a/test/dummy/config/boot.rb b/test/dummy/config/boot.rb
index eaa6ee8..4162dbb 100644
--- a/test/dummy/config/boot.rb
+++ b/test/dummy/config/boot.rb
@@ -1,4 +1,6 @@
+# frozen_string_literal: true
+
 # Set up gems listed in the Gemfile.
-ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../../../../Gemfile', __FILE__)
+ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../../../Gemfile', __dir__)
 
 require 'bundler/setup' if File.exist?(ENV['BUNDLE_GEMFILE'])
diff --git a/test/dummy/config/environment.rb b/test/dummy/config/environment.rb
index 10e0cad..bdab775 100644
--- a/test/dummy/config/environment.rb
+++ b/test/dummy/config/environment.rb
@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 # Load the Rails application.
-require File.expand_path('../application', __FILE__)
+require File.expand_path('application', __dir__)
 
 # Initialize the Rails application.
 Dummy::Application.initialize!
diff --git a/test/dummy/config/routes.rb b/test/dummy/config/routes.rb
index d426171..6ece8e7 100644
--- a/test/dummy/config/routes.rb
+++ b/test/dummy/config/routes.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 Dummy::Application.routes.draw do
   get  'test' => 'application#index'
   post 'test' => 'application#create'
diff --git a/test/test_helper.rb b/test/test_helper.rb
index b370fb7..4244a1f 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -1,5 +1,18 @@
+# frozen_string_literal: true
+
 # Configure Rails Environment
-ENV["RAILS_ENV"] = "test"
+ENV['RAILS_ENV'] = 'test'
+
+require 'simplecov'
+SimpleCov.start do
+  add_filter 'test/'
+  add_filter '.github/'
+end
+
+if ENV['CI'] == 'true'
+  require 'codecov'
+  SimpleCov.formatter = SimpleCov::Formatter::Codecov
+end
 
-require File.expand_path("../dummy/config/environment.rb",  __FILE__)
-require "rails/test_help"
+require File.expand_path('dummy/config/environment.rb', __dir__)
+require 'rails/test_help'