diff --git a/.gitignore b/.gitignore
index f927afa..b18192f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,7 @@
 /.bundle/
 /.yardoc
 /Gemfile.lock
+/gemfiles/*.lock
 /_yardoc/
 /coverage/
 /doc/
diff --git a/.rubocop.yml b/.rubocop.yml
index 3cebf67..3364cd5 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,30 +1,52 @@
 Rails: {Enabled: true}
 
-Style/Alias: {Enabled: false}
-Style/AlignParameters:
+Layout/AlignParameters:
   # Disable, till rubocop supports combination of styles.
   # Use one of this styles where appropriate, keep it clean, compact and readable.
   Enabled: false
   # EnforcedStyle:
   # - with_first_parameter
   # - with_fixed_indentation
+
+# Breaks
+#
+#   I18n.t(key,
+#     param: val,
+#     # ...
+#   )
+Layout/ClosingParenthesisIndentation: {Enabled: false}
+Layout/DotPosition: {EnforcedStyle: trailing}
+Layout/FirstParameterIndentation: {EnforcedStyle: consistent}
+# Same as Layout/ClosingParenthesisIndentation
+Layout/MultilineMethodCallBraceLayout: {Enabled: false}
+Layout/MultilineMethodCallIndentation: {EnforcedStyle: indented}
+Layout/MultilineOperationIndentation: {EnforcedStyle: indented}
+Layout/SpaceInsideHashLiteralBraces: {EnforcedStyle: no_space}
+
+# Offences named scopes and `expect {}.to change {}`.
+Lint/AmbiguousBlockAssociation: {Enabled: false}
+
+Naming/PredicateName: {Enabled: false}
+Naming/VariableNumber: {EnforcedStyle: snake_case}
+
+Style/Alias: {Enabled: false}
 Style/AndOr: {EnforcedStyle: conditionals}
-Style/ClosingParenthesisIndentation: {Enabled: false}
 Style/Documentation: {Enabled: false}
-Style/DotPosition: {EnforcedStyle: trailing}
-Style/FirstParameterIndentation: {EnforcedStyle: consistent}
 Style/IfUnlessModifier: {Enabled: false}
+
+# Consistent to other definitions.
+Style/EmptyMethod: {EnforcedStyle: expanded}
+
 Style/ModuleFunction: {Enabled: false}
-Style/MultilineMethodCallIndentation: {EnforcedStyle: indented}
-Style/MultilineOperationIndentation: {EnforcedStyle: indented}
 Style/NestedParenthesizedCalls: {Enabled: false}
-Style/PredicateName: {Enabled: false}
 Style/SignalException: {EnforcedStyle: only_raise}
-Style/SpaceInsideHashLiteralBraces: {EnforcedStyle: no_space}
 Style/TrailingCommaInArguments: {Enabled: false}
 Style/TrailingCommaInLiteral: {EnforcedStyleForMultiline: comma}
 
 Metrics/AbcSize: {Max: 21}
+# Other metrics are just enough.
+# This one offences all specs, routes and some initializers.
+Metrics/BlockLength: {Enabled: false}
 Metrics/LineLength: {Max: 100}
 Metrics/MethodLength: {Max: 30}
 Metrics/CyclomaticComplexity: {Max: 8}
diff --git a/.travis.yml b/.travis.yml
index a6dcec5..4ac3c53 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,9 +2,9 @@ language: ruby
 cache: bundler
 rvm:
   - 2.2.3
-env:
-  - RAILS=4
-  - RAILS=5
-  - RAILS=5_1
+gemfile:
+  - gemfiles/rails_42.gemfile
+  - gemfiles/rails_50.gemfile
+  - gemfiles/rails_51.gemfile
 notifications:
   email: false
diff --git a/Appraisals b/Appraisals
new file mode 100644
index 0000000..2a17e94
--- /dev/null
+++ b/Appraisals
@@ -0,0 +1,14 @@
+appraise 'rails-51' do
+  gem 'actionpack', '~> 5.1'
+  gem 'railties', '~> 5.1'
+end
+
+appraise 'rails-50' do
+  gem 'actionpack', '~> 5.0'
+  gem 'railties', '~> 5.0'
+end
+
+appraise 'rails-42' do
+  gem 'actionpack', '~> 4.2'
+  gem 'railties', '~> 4.2'
+end
diff --git a/Gemfile b/Gemfile
index b2ef288..db13674 100644
--- a/Gemfile
+++ b/Gemfile
@@ -2,24 +2,11 @@ source 'https://rubygems.org'
 gemspec
 
 group :development do
-  case ENV['RAILS']
-  when '5_1'
-    gem 'railties', '5.1.0'
-    gem 'actionpack', '5.1.0'
-  when '5'
-    gem 'railties', '5.0.2'
-    gem 'actionpack', '5.0.2'
-  when '4'
-    gem 'railties', '~> 4.2'
-    gem 'actionpack', '~> 4.2'
-  else
-    gem 'railties'
-    gem 'actionpack'
-  end
+  gem 'appraisal', '~> 2.2'
 
-  gem 'sdoc', '~> 0.4.1'
   gem 'pry', '~> 0.10.1'
   gem 'pry-byebug', '~> 3.2.0'
+  gem 'sdoc', '~> 0.4.1'
 
   gem 'telegram-bot-types', '~> 0.3.0'
 
@@ -27,7 +14,7 @@ group :development do
   gem 'rspec-its', '~> 1.1.0'
   gem 'rspec-rails', '~> 3.5.0'
 
-  gem 'rubocop', '~> 0.37.0'
+  gem 'rubocop', '~> 0.51.0'
 
   gem 'coveralls', '~> 0.8.2', require: false
 end
diff --git a/README.md b/README.md
index cd95aff..9ce6f35 100644
--- a/README.md
+++ b/README.md
@@ -507,7 +507,7 @@ Yes, it's threadsafe too.
 ## Development
 
 After checking out the repo, run `bin/setup` to install dependencies.
-Then, run `rake spec` to run the tests.
+Then, run `appraisal rake spec` to run the tests.
 You can also run `bin/console` for an interactive prompt that will allow you to experiment.
 
 To install this gem onto your local machine, run `bundle exec rake install`.
@@ -515,16 +515,6 @@ To release a new version, update the version number in `version.rb`,
 and then run `bundle exec rake release`, which will create a git tag for the version,
 push git commits and tags, and push the `.gem` file to [rubygems.org](https://rubygems.org).
 
-### Different Rails versions
-
-To setup development for specific major Rails version use:
-
-```
-RAILS=5 bundle install
-# or
-RAILS=5 bundle update
-```
-
 ## Contributing
 
 Bug reports and pull requests are welcome on GitHub at https://github.com/telegram-bot-rb/telegram-bot.
diff --git a/bin/setup b/bin/setup
index fe07d3b..b8ec1ce 100755
--- a/bin/setup
+++ b/bin/setup
@@ -3,6 +3,7 @@ set -euo pipefail
 IFS=$'\n\t'
 
 bundle install
+appraisal install
 bin/install_git_hooks
 
 # Do any other automated setup that you need to do here
diff --git a/gemfiles/rails_42.gemfile b/gemfiles/rails_42.gemfile
new file mode 100644
index 0000000..6a5d7d1
--- /dev/null
+++ b/gemfiles/rails_42.gemfile
@@ -0,0 +1,20 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "actionpack", "~> 4.2"
+gem "railties", "~> 4.2"
+
+group :development do
+  gem "pry", "~> 0.10.1"
+  gem "pry-byebug", "~> 3.2.0"
+  gem "sdoc", "~> 0.4.1"
+  gem "telegram-bot-types", "~> 0.3.0"
+  gem "rspec", "~> 3.5.0"
+  gem "rspec-its", "~> 1.1.0"
+  gem "rspec-rails", "~> 3.5.0"
+  gem "rubocop", "~> 0.51.0"
+  gem "coveralls", "~> 0.8.2", require: false
+end
+
+gemspec path: "../"
diff --git a/gemfiles/rails_50.gemfile b/gemfiles/rails_50.gemfile
new file mode 100644
index 0000000..e944c26
--- /dev/null
+++ b/gemfiles/rails_50.gemfile
@@ -0,0 +1,20 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "actionpack", "~> 5.0"
+gem "railties", "~> 5.0"
+
+group :development do
+  gem "pry", "~> 0.10.1"
+  gem "pry-byebug", "~> 3.2.0"
+  gem "sdoc", "~> 0.4.1"
+  gem "telegram-bot-types", "~> 0.3.0"
+  gem "rspec", "~> 3.5.0"
+  gem "rspec-its", "~> 1.1.0"
+  gem "rspec-rails", "~> 3.5.0"
+  gem "rubocop", "~> 0.51.0"
+  gem "coveralls", "~> 0.8.2", require: false
+end
+
+gemspec path: "../"
diff --git a/gemfiles/rails_51.gemfile b/gemfiles/rails_51.gemfile
new file mode 100644
index 0000000..3af389a
--- /dev/null
+++ b/gemfiles/rails_51.gemfile
@@ -0,0 +1,20 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "actionpack", "~> 5.1"
+gem "railties", "~> 5.1"
+
+group :development do
+  gem "pry", "~> 0.10.1"
+  gem "pry-byebug", "~> 3.2.0"
+  gem "sdoc", "~> 0.4.1"
+  gem "telegram-bot-types", "~> 0.3.0"
+  gem "rspec", "~> 3.5.0"
+  gem "rspec-its", "~> 1.1.0"
+  gem "rspec-rails", "~> 3.5.0"
+  gem "rubocop", "~> 0.51.0"
+  gem "coveralls", "~> 0.8.2", require: false
+end
+
+gemspec path: "../"
diff --git a/lib/telegram/bot/botan.rb b/lib/telegram/bot/botan.rb
index 75b3697..b135e6c 100644
--- a/lib/telegram/bot/botan.rb
+++ b/lib/telegram/bot/botan.rb
@@ -35,7 +35,7 @@ module Telegram
       def request(method, uri, query = {}, body = nil)
         res = http_request(method, uri, query.merge(token: token), body)
         status = res.status
-        return JSON.parse(res.body) if 300 > status
+        return JSON.parse(res.body) if status < 300
         result = JSON.parse(res.body) rescue nil # rubocop:disable RescueModifier
         err_msg = "#{res.reason}: #{result && result['info'] || '-'}"
         raise Error, err_msg
diff --git a/lib/telegram/bot/client.rb b/lib/telegram/bot/client.rb
index a8006ea..4220625 100644
--- a/lib/telegram/bot/client.rb
+++ b/lib/telegram/bot/client.rb
@@ -49,7 +49,7 @@ module Telegram
       def request(action, body = {})
         res = http_request("#{base_uri}#{action}", self.class.prepare_body(body))
         status = res.status
-        return JSON.parse(res.body) if 300 > status
+        return JSON.parse(res.body) if status < 300
         result = JSON.parse(res.body) rescue nil # rubocop:disable RescueModifier
         err_msg = result && result['description'] || '-'
         if result
@@ -63,7 +63,7 @@ module Telegram
       end
 
       # Splited to the sections similar to API docs.
-      %w(
+      %w[
         deleteWebhook
         getUpdates
         getWebhookInfo
@@ -124,7 +124,7 @@ module Telegram
         getGameHighScores
         sendGame
         setGameScore
-      ).each do |method|
+      ].each do |method|
         define_method(method.underscore) { |*args| request(method, *args) }
       end
 
diff --git a/lib/telegram/bot/updates_controller.rb b/lib/telegram/bot/updates_controller.rb
index a633e69..5f3509c 100644
--- a/lib/telegram/bot/updates_controller.rb
+++ b/lib/telegram/bot/updates_controller.rb
@@ -78,7 +78,7 @@ module Telegram
 
       autoload :TypedUpdate, 'telegram/bot/updates_controller/typed_update'
 
-      PAYLOAD_TYPES = %w(
+      PAYLOAD_TYPES = %w[
         message
         edited_message
         channel_post
@@ -88,7 +88,7 @@ module Telegram
         callback_query
         shipping_query
         pre_checkout_query
-      ).freeze
+      ].freeze
       CMD_REGEX = %r{\A/([a-z\d_]{,31})(@(\S+))?(\s|$)}i
       CONFLICT_CMD_REGEX = Regexp.new("^(#{PAYLOAD_TYPES.join('|')}|\\d)")
 
diff --git a/lib/telegram/bot/updates_controller/instrumentation.rb b/lib/telegram/bot/updates_controller/instrumentation.rb
index 99988bf..a2d4ce8 100644
--- a/lib/telegram/bot/updates_controller/instrumentation.rb
+++ b/lib/telegram/bot/updates_controller/instrumentation.rb
@@ -39,7 +39,7 @@ module Telegram
           Instrumentation.instrument(:respond_with, type: type) { super }
         end
 
-        %i(answer_callback_query answer_inline_query).each do |type|
+        %i[answer_callback_query answer_inline_query].each do |type|
           define_method(type) do |*args|
             Instrumentation.instrument(:respond_with, type: type) { super(*args) }
           end
diff --git a/lib/telegram/bot/updates_controller/log_subscriber.rb b/lib/telegram/bot/updates_controller/log_subscriber.rb
index eb7be10..60fe07f 100644
--- a/lib/telegram/bot/updates_controller/log_subscriber.rb
+++ b/lib/telegram/bot/updates_controller/log_subscriber.rb
@@ -17,7 +17,7 @@ module Telegram
             payload   = event.payload
             additions = UpdatesController.log_process_action(payload)
             message = "Completed in #{event.duration.round}ms"
-            message << " (#{additions.join(' | ')})" unless additions.blank?
+            message << " (#{additions.join(' | ')})" if additions.present?
             message
           end
         end
diff --git a/lib/telegram/bot/updates_controller/testing.rb b/lib/telegram/bot/updates_controller/testing.rb
index 8441aae..dd58d80 100644
--- a/lib/telegram/bot/updates_controller/testing.rb
+++ b/lib/telegram/bot/updates_controller/testing.rb
@@ -2,7 +2,7 @@ module Telegram
   module Bot
     class UpdatesController
       module Testing
-        IVARS_TO_KEEP = %i(@_session).freeze
+        IVARS_TO_KEEP = %i[@_session].freeze
 
         # Perform multiple dispatches on same instance.
         def dispatch_again(bot = nil, update = nil)
diff --git a/lib/telegram/bot/updates_poller.rb b/lib/telegram/bot/updates_poller.rb
index 8794980..5980c0f 100644
--- a/lib/telegram/bot/updates_poller.rb
+++ b/lib/telegram/bot/updates_poller.rb
@@ -50,7 +50,7 @@ module Telegram
             end
           rescue Interrupt
             @running = false
-          rescue => e
+          rescue StandardError => e
             logger.error { ([e.message] + e.backtrace).join("\n") } if logger
           end
         end
diff --git a/spec/integration_helper.rb b/spec/integration_helper.rb
index b625597..908eb0c 100644
--- a/spec/integration_helper.rb
+++ b/spec/integration_helper.rb
@@ -27,7 +27,7 @@ end
 Rails.application.initialize!
 
 # # Controllers
-%w(default other named).each do |bot_name|
+%w[default other named].each do |bot_name|
   controller = Class.new(Telegram::Bot::UpdatesController) do
     define_method :start do |*|
       respond_with :message, text: "from #{bot_name}"
diff --git a/spec/telegram/bot/client_spec.rb b/spec/telegram/bot/client_spec.rb
index caf9c63..396fee6 100644
--- a/spec/telegram/bot/client_spec.rb
+++ b/spec/telegram/bot/client_spec.rb
@@ -19,7 +19,7 @@ RSpec.describe Telegram::Bot::Client do
 
       it 'encodes nested hashes to json' do
         expected = input.dup
-        %i(c d e).each { |x| expected[x] = expected[x].to_json }
+        %i[c d e].each { |x| expected[x] = expected[x].to_json }
         should eq expected
       end
     end
@@ -35,7 +35,7 @@ RSpec.describe Telegram::Bot::Client do
     subject { described_class.new(*args) }
 
     context 'when multiple args are given' do
-      let(:args) { %w(secret superbot) }
+      let(:args) { %w[secret superbot] }
       its(:token) { should eq args[0] }
       its(:username) { should eq args[1] }
       its(:base_uri) { should include args[0] }
diff --git a/spec/telegram/bot/client_stub_spec.rb b/spec/telegram/bot/client_stub_spec.rb
index 2fe12cd..bdfe47b 100644
--- a/spec/telegram/bot/client_stub_spec.rb
+++ b/spec/telegram/bot/client_stub_spec.rb
@@ -45,7 +45,7 @@ RSpec.describe Telegram::Bot::ClientStub do
     end
 
     context 'when username and token are given' do
-      let(:args) { %w(token superbot) }
+      let(:args) { %w[token superbot] }
       its(:token) { should eq args[0] }
       its(:username) { should eq args[1] }
     end
diff --git a/spec/telegram/bot/rspec/integration_spec.rb b/spec/telegram/bot/rspec/integration_spec.rb
index c456ef1..8caa9bc 100644
--- a/spec/telegram/bot/rspec/integration_spec.rb
+++ b/spec/telegram/bot/rspec/integration_spec.rb
@@ -5,7 +5,8 @@ require 'action_dispatch/testing/integration'
 
 RSpec.describe 'Integrations helper', :telegram_bot do
   include ActionDispatch::Integration::Runner
-  def reset_template_assertion; end
+  def reset_template_assertion
+  end
 
   let(:app) do
     app = Telegram::Bot::Middleware.new(bot, controller)
@@ -38,7 +39,7 @@ RSpec.describe 'Integrations helper', :telegram_bot do
 
   describe '#dispatch_message' do
     subject { -> { dispatch_message "/start #{args.join ' '}", options } }
-    let(:args) { %w(asd qwe) }
+    let(:args) { %w[asd qwe] }
     let(:options) { {} }
     it { should respond_with_message "Start: #{args.inspect}, option: " }
 
@@ -59,7 +60,7 @@ RSpec.describe 'Integrations helper', :telegram_bot do
     it { should respond_with_message "Start: #{args.inspect}, option: " }
 
     context 'with args' do
-      let(:args) { %w(asd qwe) }
+      let(:args) { %w[asd qwe] }
       it { should respond_with_message "Start: #{args.inspect}, option: " }
     end
 
diff --git a/spec/telegram/bot/updates_controller/message_context_spec.rb b/spec/telegram/bot/updates_controller/message_context_spec.rb
index 6a3bdc0..ff0248a 100644
--- a/spec/telegram/bot/updates_controller/message_context_spec.rb
+++ b/spec/telegram/bot/updates_controller/message_context_spec.rb
@@ -65,7 +65,7 @@ RSpec.describe Telegram::Bot::UpdatesController::MessageContext do
 
       context 'when message has new command' do
         let(:text) { '/action a s d' }
-        its(:call) { should eq [:action_result, *%w(a s d)] }
+        its(:call) { should eq [:action_result, 'a', 's', 'd'] }
         it { should change { session[:context] }.to nil }
       end
     end
diff --git a/spec/telegram/bot/updates_controller/typed_update_spec.rb b/spec/telegram/bot/updates_controller/typed_update_spec.rb
index 2bca1d6..70e3a40 100644
--- a/spec/telegram/bot/updates_controller/typed_update_spec.rb
+++ b/spec/telegram/bot/updates_controller/typed_update_spec.rb
@@ -9,11 +9,11 @@ RSpec.describe Telegram::Bot::UpdatesController::TypedUpdate do
 
   context 'when `update` is a virtus model' do
     subject { controller }
-    %w(
+    %w[
       message
       inline_query
       chosen_inline_result
-    ).each do |type|
+    ].each do |type|
       context "with #{type}" do
         type_class = Telegram::Bot::Types.const_get(type.camelize)
         let(:payload_type) { type }
diff --git a/spec/telegram/bot/updates_controller_spec.rb b/spec/telegram/bot/updates_controller_spec.rb
index 0491866..4389dfb 100644
--- a/spec/telegram/bot/updates_controller_spec.rb
+++ b/spec/telegram/bot/updates_controller_spec.rb
@@ -107,7 +107,7 @@ RSpec.describe Telegram::Bot::UpdatesController do
       it { should eq [false, :unsupported_payload_type, []] }
     end
 
-    %w(message channel_post).each do |type|
+    %w[message channel_post].each do |type|
       context "when payload is edited_#{type}" do
         let(:payload_type) { "edited_#{type}" }
         it { should eq [false, payload_type, [payload]] }
@@ -123,11 +123,11 @@ RSpec.describe Telegram::Bot::UpdatesController do
         context 'with command' do
           let(:text) { "/test#{"@#{mention}" if mention} arg 1 2" }
           let(:mention) {}
-          it { should eq [true, 'test', %w(arg 1 2)] }
+          it { should eq [true, 'test', %w[arg 1 2]] }
 
           context 'with mention' do
             let(:mention) { bot.username }
-            it { should eq [true, 'test', %w(arg 1 2)] }
+            it { should eq [true, 'test', %w[arg 1 2]] }
           end
 
           context 'with mention for other bot' do
@@ -143,7 +143,7 @@ RSpec.describe Telegram::Bot::UpdatesController do
       end
     end
 
-    custom_payload_types = %w(
+    custom_payload_types = %w[
       message
       edited_message
       channel_post
@@ -151,7 +151,7 @@ RSpec.describe Telegram::Bot::UpdatesController do
       inline_query
       chosen_inline_result
       callback_query
-    )
+    ]
     (described_class::PAYLOAD_TYPES - custom_payload_types).each do |type|
       context "when payload is #{type}" do
         let(:payload_type) { type }
@@ -163,11 +163,11 @@ RSpec.describe Telegram::Bot::UpdatesController do
   context 'when `update` is a virtus model' do
     subject { controller }
     let(:update) { Telegram::Bot::Types::Update.new(super()) }
-    %w(
+    %w[
       message
       inline_query
       chosen_inline_result
-    ).each do |type|
+    ].each do |type|
       context "with #{type}" do
         type_class = Telegram::Bot::Types.const_get(type.camelize)
         let(:payload_type) { type }
@@ -194,7 +194,7 @@ RSpec.describe Telegram::Bot::UpdatesController do
 
   describe '#process' do
     subject { -> { controller.process(:action, *args) } }
-    let(:args) { [:arg1, :arg2] }
+    let(:args) { %i[arg1 arg2] }
     let(:controller_class) do
       Class.new(described_class) do
         attr_reader :acted, :hooked
diff --git a/telegram-bot.gemspec b/telegram-bot.gemspec
index 09ea73c..427a3f7 100644
--- a/telegram-bot.gemspec
+++ b/telegram-bot.gemspec
@@ -1,4 +1,3 @@
-# coding: utf-8
 lib = File.expand_path('../lib', __FILE__)
 $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 require 'telegram/bot/version'
@@ -20,9 +19,10 @@ Gem::Specification.new do |spec|
 
   spec.required_ruby_version = '~> 2.0'
 
-  spec.add_dependency 'activesupport', '>= 4.0', '< 5.2'
   spec.add_dependency 'actionpack', '>= 4.0', '< 5.2'
+  spec.add_dependency 'activesupport', '>= 4.0', '< 5.2'
   spec.add_dependency 'httpclient', '~> 2.7'
+
   spec.add_development_dependency 'bundler', '~> 1.11'
   spec.add_development_dependency 'rake', '~> 10.0'
 end