diff --git a/.rubocop.yml b/.rubocop.yml
index 42f280c..795ded7 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,18 +1,23 @@
-inherit_from: .rubocop_todo.yml
+require:
+  - rubocop-rails
+
 AllCops:
   DisplayCopNames: true
-  TargetRubyVersion: 2.4
-  Include:
-    - Rakefile
-    - lib/**/*.rake
+  TargetRubyVersion: 2.7
+  SuggestExtensions: false
+  NewCops: enable
   Exclude:
-    - Gemfile
-    - Appraisals
-    - rails-letsencrypt.gemspec
-    - lib/generators/lets_encrypt/templates/migration.rb
+    - gemfiles/*
     - spec/dummy/**/*
+    - lib/generators/lets_encrypt/templates/*
+
 Rails:
   Enabled: true
+
+Naming/FileName:
+  Exclude:
+    - lib/rails-letsencrypt.rb
+
 Metrics/BlockLength:
   Exclude:
     - spec/**/*.rb
diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
deleted file mode 100644
index 84a0984..0000000
--- a/.rubocop_todo.yml
+++ /dev/null
@@ -1,61 +0,0 @@
-# This configuration was generated by
-# `rubocop --auto-gen-config`
-# on 2017-05-11 16:33:13 +0800 using RuboCop version 0.48.1.
-# The point is for the user to remove these configuration records
-# one by one as the offenses are removed from the code base.
-# Note that changes in the inspected code, or installation of new
-# versions of RuboCop, may require this file to be generated again.
-
-# Offense count: 1
-Lint/AmbiguousBlockAssociation:
-  Exclude:
-    - 'app/models/lets_encrypt/certificate.rb'
-
-# Offense count: 4
-# Configuration parameters: AllowHeredoc, AllowURI, URISchemes, IgnoreCopDirectives, IgnoredPatterns.
-# URISchemes: http, https
-Metrics/LineLength:
-  Max: 92
-
-# Offense count: 1
-# Cop supports --auto-correct.
-Style/BlockComments:
-  Exclude:
-    - 'spec/spec_helper.rb'
-
-# Offense count: 1
-# Configuration parameters: ExpectMatchingDefinition, Regex, IgnoreExecutableScripts, AllowedAcronyms.
-# AllowedAcronyms: CLI, DSL, ACL, API, ASCII, CPU, CSS, DNS, EOF, GUID, HTML, HTTP, HTTPS, ID, IP, JSON, LHS, QPS, RAM, RHS, RPC, SLA, SMTP, SQL, SSH, TCP, TLS, TTL, UDP, UI, UID, UUID, URI, URL, UTF8, VM, XML, XMPP, XSRF, XSS
-Style/FileName:
-  Exclude:
-    - 'lib/rails-letsencrypt.rb'
-
-# Offense count: 1
-# Cop supports --auto-correct.
-Style/MutableConstant:
-  Exclude:
-    - 'lib/letsencrypt/version.rb'
-
-# Offense count: 1
-# Cop supports --auto-correct.
-# Configuration parameters: SupportedStyles.
-# SupportedStyles: use_perl_names, use_english_names
-Style/SpecialGlobalVars:
-  EnforcedStyle: use_perl_names
-
-# Offense count: 18
-# Cop supports --auto-correct.
-# Configuration parameters: EnforcedStyle, SupportedStyles, ConsistentQuotesInMultiline.
-# SupportedStyles: single_quotes, double_quotes
-Style/StringLiterals:
-  Exclude:
-    - 'rails-letsencrypt.gemspec'
-    - 'spec/rails_helper.rb'
-
-# Offense count: 1
-# Cop supports --auto-correct.
-# Configuration parameters: EnforcedStyle, SupportedStyles.
-# SupportedStyles: final_newline, final_blank_line
-Style/TrailingBlankLines:
-  Exclude:
-    - 'rails-letsencrypt.gemspec'
diff --git a/Appraisals b/Appraisals
index 0cf81bc..8312aee 100644
--- a/Appraisals
+++ b/Appraisals
@@ -1,21 +1,21 @@
 # frozen_string_literal: true
 
 appraise 'rails6' do
-  gem "railties", "~> 6.1"
-  gem "actionmailer", "~> 6.1"
-  gem "actionpack", "~> 6.1"
-  gem "actionview", "~> 6.1"
-  gem "activemodel", "~> 6.1"
-  gem "activerecord", "~> 6.1"
-  gem "activesupport", "~> 6.1"
+  gem 'railties', '~> 6.1'
+  gem 'actionmailer', '~> 6.1'
+  gem 'actionpack', '~> 6.1'
+  gem 'actionview', '~> 6.1'
+  gem 'activemodel', '~> 6.1'
+  gem 'activerecord', '~> 6.1'
+  gem 'activesupport', '~> 6.1'
 end
 
 appraise 'rails7' do
-  gem "railties", "~> 7"
-  gem "actionmailer", "~> 7"
-  gem "actionpack", "~> 7"
-  gem "actionview", "~> 7"
-  gem "activemodel", "~> 7"
-  gem "activerecord", "~> 7"
-  gem "activesupport", "~> 7"
+  gem 'railties', '~> 7'
+  gem 'actionmailer', '~> 7'
+  gem 'actionpack', '~> 7'
+  gem 'actionview', '~> 7'
+  gem 'activemodel', '~> 7'
+  gem 'activerecord', '~> 7'
+  gem 'activesupport', '~> 7'
 end
diff --git a/Gemfile b/Gemfile
index fb78959..5f8ea76 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,4 +1,5 @@
 # frozen_string_literal: true
+
 source 'https://rubygems.org'
 
 # Declare your gem's dependencies in lets_encrypt.gemspec.
@@ -13,4 +14,9 @@ gemspec
 
 # To use a debugger
 # gem 'byebug', group: [:development, :test]
+gem 'appraisal'
+gem 'rspec-rails'
+gem 'rubocop', '~> 1.57.2'
+gem 'rubocop-rails'
+gem 'simplecov', '~> 0.16.1'
 gem 'sqlite3'
diff --git a/app/controllers/lets_encrypt/verifications_controller.rb b/app/controllers/lets_encrypt/verifications_controller.rb
index 5453d56..fe09304 100644
--- a/app/controllers/lets_encrypt/verifications_controller.rb
+++ b/app/controllers/lets_encrypt/verifications_controller.rb
@@ -7,7 +7,8 @@ module LetsEncrypt
   class VerificationsController < ApplicationController
     def show
       return render_verification_string if certificate.present?
-      render plain: 'Verification not found', status: 404
+
+      render plain: 'Verification not found', status: :not_found
     end
 
     protected
diff --git a/app/jobs/lets_encrypt/renew_certificates_job.rb b/app/jobs/lets_encrypt/renew_certificates_job.rb
index 4b543aa..87f1f76 100644
--- a/app/jobs/lets_encrypt/renew_certificates_job.rb
+++ b/app/jobs/lets_encrypt/renew_certificates_job.rb
@@ -8,6 +8,7 @@ class RenewCertificatesJob < ApplicationJob
     def perform
       LetsEncrypt.certificate_model.renewable.each do |certificate|
         next if certificate.renew
+
         certificate.update(renew_after: 1.day.from_now)
       end
     end
diff --git a/app/models/concerns/lets_encrypt/certificate_issuable.rb b/app/models/concerns/lets_encrypt/certificate_issuable.rb
index a07ffa2..c0863a7 100644
--- a/app/models/concerns/lets_encrypt/certificate_issuable.rb
+++ b/app/models/concerns/lets_encrypt/certificate_issuable.rb
@@ -9,9 +9,7 @@ module CertificateIssuable
     def issue
       logger.info "Getting certificate for #{domain}"
       create_certificate
-      # rubocop:disable Metrics/LineLength
       logger.info "Certificate issued for #{domain} (expires on #{expires_at}, will renew after #{renew_after})"
-      # rubocop:enable Metrics/LineLength
       true
     end
 
@@ -30,12 +28,16 @@ def create_certificate
       order.finalize(csr: csr)
       sleep 1 while order.status == 'processing'
       fullchain = order.certificate.split("\n\n")
+      assign_new_certificate(fullchain)
+      save!
+    end
+
+    def assign_new_certificate(fullchain)
       cert = OpenSSL::X509::Certificate.new(fullchain.shift)
       self.certificate = cert.to_pem
       self.intermediaries = fullchain.join("\n\n")
       self.expires_at = cert.not_after
       self.renew_after = (expires_at - 1.month) + rand(10).days
-      save!
     end
   end
 end
diff --git a/app/models/concerns/lets_encrypt/certificate_verifiable.rb b/app/models/concerns/lets_encrypt/certificate_verifiable.rb
index 0b2db5d..22a25a3 100644
--- a/app/models/concerns/lets_encrypt/certificate_verifiable.rb
+++ b/app/models/concerns/lets_encrypt/certificate_verifiable.rb
@@ -52,16 +52,16 @@ def check_verify_status
       true
     end
 
-    def retry_on_verify_error(e)
+    def retry_on_verify_error(error)
       @retries ||= 0
-      if e.is_a?(Acme::Client::Error::BadNonce) && @retries < 5
+      if error.is_a?(Acme::Client::Error::BadNonce) && @retries < 5
         @retries += 1
         logger.info "#{domain}: Bad nounce encountered. Retrying (#{@retries} of 5 attempts)"
         sleep 1
         verify
       else
         logger.info "#{domain}: Error: #{e.class} (#{e.message})"
-        return false
+        false
       end
     end
   end
diff --git a/app/models/lets_encrypt/certificate.rb b/app/models/lets_encrypt/certificate.rb
index 9cc8489..fafafdc 100644
--- a/app/models/lets_encrypt/certificate.rb
+++ b/app/models/lets_encrypt/certificate.rb
@@ -22,7 +22,7 @@ module LetsEncrypt
   #  index_letsencrypt_certificates_on_domain       (domain)
   #  index_letsencrypt_certificates_on_renew_after  (renew_after)
   #
-  class Certificate < ActiveRecord::Base
+  class Certificate < ApplicationRecord
     include CertificateVerifiable
     include CertificateIssuable
 
@@ -33,8 +33,8 @@ class Certificate < ActiveRecord::Base
     scope :expired, -> { where('expires_at <= ?', Time.zone.now) }
 
     before_create -> { self.key = OpenSSL::PKey::RSA.new(4096).to_s }
-    after_save -> { save_to_redis }, if: -> { LetsEncrypt.config.use_redis? && active? }
     after_destroy -> { delete_from_redis }, if: -> { LetsEncrypt.config.use_redis? && active? }
+    after_save -> { save_to_redis }, if: -> { LetsEncrypt.config.use_redis? && active? }
 
     # Returns false if certificate is not issued.
     #
diff --git a/bin/rails b/bin/rails
index b685479..b5bbca4 100755
--- a/bin/rails
+++ b/bin/rails
@@ -4,11 +4,11 @@
 # This command will automatically be run when you run "rails" with Rails gems
 # installed from the root of your application.
 
-ENGINE_ROOT = File.expand_path('../..', __FILE__)
-ENGINE_PATH = File.expand_path('../../lib/letsencrypt/engine', __FILE__)
+ENGINE_ROOT = File.expand_path('..', __dir__)
+ENGINE_PATH = File.expand_path('../lib/letsencrypt/engine', __dir__)
 
 # 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'])
 
 require 'rails/all'
diff --git a/gemfiles/rails6.gemfile b/gemfiles/rails6.gemfile
index 09e4545..da92a6e 100644
--- a/gemfiles/rails6.gemfile
+++ b/gemfiles/rails6.gemfile
@@ -2,6 +2,11 @@
 
 source "https://rubygems.org"
 
+gem "appraisal"
+gem "rspec-rails"
+gem "rubocop", "~> 1.57.2"
+gem "rubocop-rails"
+gem "simplecov", "~> 0.16.1"
 gem "sqlite3"
 gem "railties", "~> 6.1"
 gem "actionmailer", "~> 6.1"
diff --git a/gemfiles/rails6.gemfile.lock b/gemfiles/rails6.gemfile.lock
index 44867b6..4f90a97 100644
--- a/gemfiles/rails6.gemfile.lock
+++ b/gemfiles/rails6.gemfile.lock
@@ -56,12 +56,13 @@ GEM
       bundler
       rake
       thor (>= 0.14.0)
-    base64 (0.1.1)
+    ast (2.4.2)
+    base64 (0.2.0)
     builder (3.2.4)
     concurrent-ruby (1.2.2)
     connection_pool (2.4.1)
     crass (1.0.6)
-    date (3.3.3)
+    date (3.3.4)
     diff-lcs (1.5.0)
     docile (1.4.0)
     erubi (1.12.0)
@@ -77,6 +78,7 @@ GEM
     i18n (1.14.1)
       concurrent-ruby (~> 1.0)
     json (2.6.3)
+    language_server-protocol (3.17.0.3)
     loofah (2.21.4)
       crass (~> 1.0.2)
       nokogiri (>= 1.12.0)
@@ -87,24 +89,24 @@ GEM
       net-smtp
     method_source (1.0.0)
     mini_mime (1.1.5)
-    mini_portile2 (2.8.5)
     minitest (5.20.0)
     net-imap (0.4.4)
       date
       net-protocol
     net-pop (0.1.2)
       net-protocol
-    net-protocol (0.2.1)
+    net-protocol (0.2.2)
       timeout
     net-smtp (0.4.0)
       net-protocol
-    nokogiri (1.15.4)
-      mini_portile2 (~> 2.8.2)
-      racc (~> 1.4)
     nokogiri (1.15.4-x86_64-darwin)
       racc (~> 1.4)
     nokogiri (1.15.4-x86_64-linux)
       racc (~> 1.4)
+    parallel (1.23.0)
+    parser (3.2.2.4)
+      ast (~> 2.4.1)
+      racc
     racc (1.7.3)
     rack (2.2.8)
     rack-test (2.1.0)
@@ -122,11 +124,14 @@ GEM
       method_source
       rake (>= 12.2)
       thor (~> 1.0)
+    rainbow (3.1.1)
     rake (13.1.0)
     redis (5.0.8)
       redis-client (>= 0.17.0)
     redis-client (0.18.0)
       connection_pool
+    regexp_parser (2.8.2)
+    rexml (3.2.6)
     rspec-core (3.12.2)
       rspec-support (~> 3.12.0)
     rspec-expectations (3.12.3)
@@ -144,24 +149,40 @@ GEM
       rspec-mocks (~> 3.12)
       rspec-support (~> 3.12)
     rspec-support (3.12.1)
+    rubocop (1.57.2)
+      json (~> 2.3)
+      language_server-protocol (>= 3.17.0)
+      parallel (~> 1.10)
+      parser (>= 3.2.2.4)
+      rainbow (>= 2.2.2, < 4.0)
+      regexp_parser (>= 1.8, < 3.0)
+      rexml (>= 3.2.5, < 4.0)
+      rubocop-ast (>= 1.28.1, < 2.0)
+      ruby-progressbar (~> 1.7)
+      unicode-display_width (>= 2.4.0, < 3.0)
+    rubocop-ast (1.30.0)
+      parser (>= 3.2.1.0)
+    rubocop-rails (2.22.1)
+      activesupport (>= 4.2.0)
+      rack (>= 1.1)
+      rubocop (>= 1.33.0, < 2.0)
+    ruby-progressbar (1.13.0)
     ruby2_keywords (0.0.5)
     simplecov (0.16.1)
       docile (~> 1.1)
       json (>= 1.8, < 3)
       simplecov-html (~> 0.10.0)
     simplecov-html (0.10.2)
-    sqlite3 (1.6.8)
-      mini_portile2 (~> 2.8.0)
     sqlite3 (1.6.8-x86_64-darwin)
     sqlite3 (1.6.8-x86_64-linux)
     thor (1.3.0)
-    timeout (0.4.0)
+    timeout (0.4.1)
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
+    unicode-display_width (2.5.0)
     zeitwerk (2.6.12)
 
 PLATFORMS
-  ruby
   x86_64-darwin-22
   x86_64-linux
 
@@ -176,6 +197,8 @@ DEPENDENCIES
   rails-letsencrypt!
   railties (~> 6.1)
   rspec-rails
+  rubocop (~> 1.57.2)
+  rubocop-rails
   simplecov (~> 0.16.1)
   sqlite3
 
diff --git a/gemfiles/rails7.gemfile b/gemfiles/rails7.gemfile
index 5cd5d6a..7d4b25d 100644
--- a/gemfiles/rails7.gemfile
+++ b/gemfiles/rails7.gemfile
@@ -2,6 +2,11 @@
 
 source "https://rubygems.org"
 
+gem "appraisal"
+gem "rspec-rails"
+gem "rubocop", "~> 1.57.2"
+gem "rubocop-rails"
+gem "simplecov", "~> 0.16.1"
 gem "sqlite3"
 gem "railties", "~> 7"
 gem "actionmailer", "~> 7"
diff --git a/gemfiles/rails7.gemfile.lock b/gemfiles/rails7.gemfile.lock
index 78c35b4..65f75bb 100644
--- a/gemfiles/rails7.gemfile.lock
+++ b/gemfiles/rails7.gemfile.lock
@@ -66,16 +66,17 @@ GEM
       bundler
       rake
       thor (>= 0.14.0)
-    base64 (0.1.1)
+    ast (2.4.2)
+    base64 (0.2.0)
     bigdecimal (3.1.4)
     builder (3.2.4)
     concurrent-ruby (1.2.2)
     connection_pool (2.4.1)
     crass (1.0.6)
-    date (3.3.3)
+    date (3.3.4)
     diff-lcs (1.5.0)
     docile (1.4.0)
-    drb (2.1.1)
+    drb (2.2.0)
       ruby2_keywords
     erubi (1.12.0)
     faraday (2.7.11)
@@ -94,6 +95,7 @@ GEM
       rdoc
       reline (>= 0.3.8)
     json (2.6.3)
+    language_server-protocol (3.17.0.3)
     loofah (2.21.4)
       crass (~> 1.0.2)
       nokogiri (>= 1.12.0)
@@ -103,7 +105,6 @@ GEM
       net-pop
       net-smtp
     mini_mime (1.1.5)
-    mini_portile2 (2.8.5)
     minitest (5.20.0)
     mutex_m (0.2.0)
     net-imap (0.4.4)
@@ -111,17 +112,18 @@ GEM
       net-protocol
     net-pop (0.1.2)
       net-protocol
-    net-protocol (0.2.1)
+    net-protocol (0.2.2)
       timeout
     net-smtp (0.4.0)
       net-protocol
-    nokogiri (1.15.4)
-      mini_portile2 (~> 2.8.2)
-      racc (~> 1.4)
     nokogiri (1.15.4-x86_64-darwin)
       racc (~> 1.4)
     nokogiri (1.15.4-x86_64-linux)
       racc (~> 1.4)
+    parallel (1.23.0)
+    parser (3.2.2.4)
+      ast (~> 2.4.1)
+      racc
     psych (5.1.1.1)
       stringio
     racc (1.7.3)
@@ -148,6 +150,7 @@ GEM
       rake (>= 12.2)
       thor (~> 1.0, >= 1.2.2)
       zeitwerk (~> 2.6)
+    rainbow (3.1.1)
     rake (13.1.0)
     rdoc (6.6.0)
       psych (>= 4.0.0)
@@ -155,8 +158,10 @@ GEM
       redis-client (>= 0.17.0)
     redis-client (0.18.0)
       connection_pool
+    regexp_parser (2.8.2)
     reline (0.3.9)
       io-console (~> 0.5)
+    rexml (3.2.6)
     rspec-core (3.12.2)
       rspec-support (~> 3.12.0)
     rspec-expectations (3.12.3)
@@ -174,26 +179,42 @@ GEM
       rspec-mocks (~> 3.12)
       rspec-support (~> 3.12)
     rspec-support (3.12.1)
+    rubocop (1.57.2)
+      json (~> 2.3)
+      language_server-protocol (>= 3.17.0)
+      parallel (~> 1.10)
+      parser (>= 3.2.2.4)
+      rainbow (>= 2.2.2, < 4.0)
+      regexp_parser (>= 1.8, < 3.0)
+      rexml (>= 3.2.5, < 4.0)
+      rubocop-ast (>= 1.28.1, < 2.0)
+      ruby-progressbar (~> 1.7)
+      unicode-display_width (>= 2.4.0, < 3.0)
+    rubocop-ast (1.30.0)
+      parser (>= 3.2.1.0)
+    rubocop-rails (2.22.1)
+      activesupport (>= 4.2.0)
+      rack (>= 1.1)
+      rubocop (>= 1.33.0, < 2.0)
+    ruby-progressbar (1.13.0)
     ruby2_keywords (0.0.5)
     simplecov (0.16.1)
       docile (~> 1.1)
       json (>= 1.8, < 3)
       simplecov-html (~> 0.10.0)
     simplecov-html (0.10.2)
-    sqlite3 (1.6.8)
-      mini_portile2 (~> 2.8.0)
     sqlite3 (1.6.8-x86_64-darwin)
     sqlite3 (1.6.8-x86_64-linux)
     stringio (3.0.8)
     thor (1.3.0)
-    timeout (0.4.0)
+    timeout (0.4.1)
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
+    unicode-display_width (2.5.0)
     webrick (1.8.1)
     zeitwerk (2.6.12)
 
 PLATFORMS
-  ruby
   x86_64-darwin-22
   x86_64-linux
 
@@ -208,6 +229,8 @@ DEPENDENCIES
   rails-letsencrypt!
   railties (~> 7)
   rspec-rails
+  rubocop (~> 1.57.2)
+  rubocop-rails
   simplecov (~> 0.16.1)
   sqlite3
 
diff --git a/lib/generators/lets_encrypt/install_generator.rb b/lib/generators/lets_encrypt/install_generator.rb
index 171e45d..658094b 100644
--- a/lib/generators/lets_encrypt/install_generator.rb
+++ b/lib/generators/lets_encrypt/install_generator.rb
@@ -10,7 +10,7 @@ module Generators
     class InstallGenerator < ::Rails::Generators::Base
       include ::Rails::Generators::Migration
 
-      source_root File.expand_path('../templates', __FILE__)
+      source_root File.expand_path('templates', __dir__)
 
       def self.next_migration_number(path)
         ActiveRecord::Generators::Base.next_migration_number(path)
diff --git a/lib/generators/lets_encrypt/register_generator.rb b/lib/generators/lets_encrypt/register_generator.rb
index 33b2781..e496c5d 100644
--- a/lib/generators/lets_encrypt/register_generator.rb
+++ b/lib/generators/lets_encrypt/register_generator.rb
@@ -26,26 +26,24 @@ def setup_environment
       end
 
       def generate_key
-        # rubocop:disable Metrics/LineLength
         key_path = ask("Where you to save private key [#{LetsEncrypt.private_key_path}]:", path: true)
-        # rubocop:enable Metrics/LineLength
         key_path = LetsEncrypt.private_key_path if key_path.blank?
 
         return unless file_collision(key_path)
-        FileUtils.rm(key_path) if File.exist?(key_path)
+
+        FileUtils.rm_f(key_path)
         LetsEncrypt.config.use_env_key = false
         LetsEncrypt.config.private_key_path = key_path
 
         LetsEncrypt.load_private_key
 
-        # rubocop:disable Metrics/LineLength
         say "Your privated key is saved in #{key_path}, make sure setup configure for your rails.", :yellow
-        # rubocop:enable Metrics/LineLength
       end
 
       def register_email
         email = ask('What email you want to register:')
         return say('Email is inavlid!', :red) if email.blank?
+
         LetsEncrypt.register(email)
         say 'Register successed, don\'t forget backup your private key', :green
       end
diff --git a/lib/letsencrypt.rb b/lib/letsencrypt.rb
index 5d8f378..e2b124f 100644
--- a/lib/letsencrypt.rb
+++ b/lib/letsencrypt.rb
@@ -32,14 +32,15 @@ def private_key
     end
 
     def load_private_key
-      return ENV['LETSENCRYPT_PRIVATE_KEY'] if config.use_env_key
+      return ENV.fetch('LETSENCRYPT_PRIVATE_KEY', nil) if config.use_env_key
       return File.open(private_key_path) if File.exist?(private_key_path)
+
       generate_private_key
     end
 
     # Get current using Let's Encrypt endpoint
     def directory
-      @endpoint ||= config.use_staging? ? ENDPOINT_STAGING : ENDPOINT
+      @directory ||= config.use_staging? ? ENDPOINT_STAGING : ENDPOINT
     end
 
     # Register a Let's Encrypt account
@@ -56,12 +57,12 @@ def register(email)
     end
 
     def private_key_path
-      config.private_key_path || Rails.root.join('config', 'letsencrypt.key')
+      config.private_key_path || Rails.root.join('config/letsencrypt.key')
     end
 
     def generate_private_key
       key = OpenSSL::PKey::RSA.new(4096)
-      File.open(private_key_path, 'w') { |f| f.write(key.to_s) }
+      File.write(private_key_path, key.to_s)
       logger.info "Created new private key for Let's Encrypt"
       key
     end
diff --git a/lib/letsencrypt/logger_proxy.rb b/lib/letsencrypt/logger_proxy.rb
index 875b29b..816435b 100644
--- a/lib/letsencrypt/logger_proxy.rb
+++ b/lib/letsencrypt/logger_proxy.rb
@@ -15,10 +15,10 @@ def add_tags(*tags)
       @tags = @tags.uniq
     end
 
-    def tag(logger)
+    def tag(logger, &block)
       if logger.respond_to?(:tagged)
         current_tags = tags - logger.formatter.current_tags
-        logger.tagged(*current_tags) { yield }
+        logger.tagged(*current_tags, &block)
       else
         yield
       end
diff --git a/lib/letsencrypt/redis.rb b/lib/letsencrypt/redis.rb
index 5bb2045..ac402b8 100644
--- a/lib/letsencrypt/redis.rb
+++ b/lib/letsencrypt/redis.rb
@@ -11,6 +11,7 @@ def connection
       # Save certificate into redis.
       def save(cert)
         return unless cert.key.present? && cert.bundle.present?
+
         LetsEncrypt.logger.info "Save #{cert.domain}'s certificate (bundle) to redis"
         connection.set "#{cert.domain}.key", cert.key
         connection.set "#{cert.domain}.crt", cert.bundle
@@ -19,6 +20,7 @@ def save(cert)
       # Delete certificate from redis.
       def delete(cert)
         return unless cert.key.present? && cert.certificate.present?
+
         LetsEncrypt.logger.info "Delete #{cert.domain}'s certificate from redis"
         connection.del "#{cert.domain}.key"
         connection.del "#{cert.domain}.crt"
diff --git a/lib/tasks/letsencrypt_tasks.rake b/lib/tasks/letsencrypt_tasks.rake
index 8b31132..eb30233 100644
--- a/lib/tasks/letsencrypt_tasks.rake
+++ b/lib/tasks/letsencrypt_tasks.rake
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 namespace :letsencrypt do
-  desc "Renew certificates that already expired or expiring soon"
+  desc 'Renew certificates that already expired or expiring soon'
   task renew: :environment do
     count = 0
     failed = 0
diff --git a/rails-letsencrypt.gemspec b/rails-letsencrypt.gemspec
index 5cd7ca4..fd7ac85 100644
--- a/rails-letsencrypt.gemspec
+++ b/rails-letsencrypt.gemspec
@@ -1,35 +1,33 @@
 # frozen_string_literal: true
 
-$:.push File.expand_path("../lib", __FILE__)
+$LOAD_PATH.push File.expand_path('lib', __dir__)
 
 # Maintain your gem's version:
-require "letsencrypt/version"
+require 'letsencrypt/version'
 
 # Describe your gem and declare its dependencies:
 Gem::Specification.new do |s|
-  s.name        = "rails-letsencrypt"
+  s.name        = 'rails-letsencrypt'
   s.version     = LetsEncrypt::VERSION
-  s.authors     = ["蒼時弦也"]
-  s.email       = ["elct9620@frost.tw"]
-  s.homepage    = "https://github.com/elct9620/rails-letsencrypt"
+  s.authors     = ['蒼時弦也']
+  s.email       = ['elct9620@frost.tw']
+  s.homepage    = 'https://github.com/elct9620/rails-letsencrypt'
   s.summary     = "The Let's Encrypt certificate manager for rails"
   s.description = "The Let's Encrypt certificate manager for rails"
-  s.license     = "MIT"
+  s.license     = 'MIT'
 
-  s.files = Dir["{app,config,db,lib}/**/*", "MIT-LICENSE", "Rakefile", "README.md"]
-  s.require_paths = ["lib"]
+  s.files = Dir['{app,config,db,lib}/**/*', 'MIT-LICENSE', 'Rakefile', 'README.md']
+  s.require_paths = ['lib']
 
-  s.add_dependency "railties", ">= 6.1"
-  s.add_dependency "actionmailer", ">= 6.1"
-  s.add_dependency "actionpack", ">= 6.1"
-  s.add_dependency "actionview", ">= 6.1"
-  s.add_dependency "activemodel", ">= 6.1"
-  s.add_dependency "activerecord", ">= 6.1"
-  s.add_dependency "activesupport", ">= 6.1"
-  s.add_dependency "acme-client", "~> 2.0.0"
-  s.add_dependency "redis"
-
-  s.add_development_dependency "appraisal"
-  s.add_development_dependency "rspec-rails"
-  s.add_development_dependency "simplecov", "~> 0.16.1"
+  s.required_ruby_version = '>= 2.7.0'
+  s.add_dependency 'acme-client', '~> 2.0.0'
+  s.add_dependency 'actionmailer', '>= 6.1'
+  s.add_dependency 'actionpack', '>= 6.1'
+  s.add_dependency 'actionview', '>= 6.1'
+  s.add_dependency 'activemodel', '>= 6.1'
+  s.add_dependency 'activerecord', '>= 6.1'
+  s.add_dependency 'activesupport', '>= 6.1'
+  s.add_dependency 'railties', '>= 6.1'
+  s.add_dependency 'redis'
+  s.metadata['rubygems_mfa_required'] = 'true'
 end
diff --git a/spec/controllers/lets_encrypt/verifications_controller_spec.rb b/spec/controllers/lets_encrypt/verifications_controller_spec.rb
index d2d275a..dcb1569 100644
--- a/spec/controllers/lets_encrypt/verifications_controller_spec.rb
+++ b/spec/controllers/lets_encrypt/verifications_controller_spec.rb
@@ -4,7 +4,9 @@
 
 RSpec.describe LetsEncrypt::VerificationsController, type: :controller do
   routes { LetsEncrypt::Engine.routes }
-  class OtherModel < LetsEncrypt::Certificate
+
+  before do
+    stub_const('LetsEncrypt::Certificate', Class.new(LetsEncrypt::Certificate))
   end
 
   it 'returns 404 status when no valid verification path found' do
@@ -12,7 +14,6 @@ class OtherModel < LetsEncrypt::Certificate
     expect(response.status).to eq(404)
   end
 
-
   describe 'has certificate' do
     context 'with default model' do
       let!(:certificate) do
diff --git a/spec/letsencrypt/configuration_spec.rb b/spec/letsencrypt/configuration_spec.rb
index d5a2842..e1520fd 100644
--- a/spec/letsencrypt/configuration_spec.rb
+++ b/spec/letsencrypt/configuration_spec.rb
@@ -18,15 +18,16 @@
   end
 
   describe 'customize certificate model' do
-    class OtherModel < LetsEncrypt::Certificate
-      after_update :success
+    before(:each) do
+      stub_const('OtherModel', Class.new(LetsEncrypt::Certificate))
 
-      def success
-        'success'
+      OtherModel.after_update :success
+      OtherModel.class_eval do
+        def success
+          'success'
+        end
       end
-    end
 
-    before(:each) do
       LetsEncrypt.config.certificate_model = 'OtherModel'
       allow(LetsEncrypt).to receive(:certificate_model).and_return(OtherModel)
       LetsEncrypt.certificate_model.create(
diff --git a/spec/letsencrypt/generators/lets_encrypt/install_generator_spec.rb b/spec/letsencrypt/generators/lets_encrypt/install_generator_spec.rb
index fceb86b..26e4594 100644
--- a/spec/letsencrypt/generators/lets_encrypt/install_generator_spec.rb
+++ b/spec/letsencrypt/generators/lets_encrypt/install_generator_spec.rb
@@ -6,7 +6,7 @@
 
 RSpec.describe LetsEncrypt::Generators::InstallGenerator do
   before(:all) do
-    @dummy_class = Class.new(::Rails::Generators::TestCase) do
+    @dummy_class = Class.new(Rails::Generators::TestCase) do
       tests LetsEncrypt::Generators::InstallGenerator
       destination Rails.root.join('tmp')
     end
@@ -17,6 +17,6 @@
   end
 
   it do
-    @generator.assert_migration "db/migrate/create_letsencrypt_certificates.rb", /def change/
+    @generator.assert_migration 'db/migrate/create_letsencrypt_certificates.rb', /def change/
   end
 end
diff --git a/spec/letsencrypt/generators/lets_encrypt/register_generator_spec.rb b/spec/letsencrypt/generators/lets_encrypt/register_generator_spec.rb
index 21b8baf..c06db28 100644
--- a/spec/letsencrypt/generators/lets_encrypt/register_generator_spec.rb
+++ b/spec/letsencrypt/generators/lets_encrypt/register_generator_spec.rb
@@ -6,7 +6,7 @@
 
 RSpec.describe LetsEncrypt::Generators::RegisterGenerator do
   before(:all) do
-    @dummy_class = Class.new(::Rails::Generators::TestCase) do
+    @dummy_class = Class.new(Rails::Generators::TestCase) do
       tests LetsEncrypt::Generators::RegisterGenerator
       destination Rails.root.join('tmp')
     end
diff --git a/spec/letsencrypt/redis_spec.rb b/spec/letsencrypt/redis_spec.rb
index 1cd2d93..b020f54 100644
--- a/spec/letsencrypt/redis_spec.rb
+++ b/spec/letsencrypt/redis_spec.rb
@@ -3,25 +3,25 @@
 require 'rails_helper'
 
 RSpec.describe LetsEncrypt::Redis do
-  let(:redis) { double(::Redis) }
+  let(:redis) { double(Redis) }
   let(:domain) { 'example.com' }
   let(:certificate) do
     LetsEncrypt::Certificate.new(domain: domain, key: '', certificate: '')
   end
 
   before(:each) do
-    allow(::Redis).to receive(:new).and_return(redis)
+    allow(Redis).to receive(:new).and_return(redis)
   end
 
   after do
     # Reset connection because redis double will work only for single example
-    LetsEncrypt::Redis.instance_variable_set("@connection", nil)
+    LetsEncrypt::Redis.instance_variable_set('@connection', nil)
   end
 
   describe '#save' do
     it 'saves certificate into redis' do
-      certificate.key = "KEY"
-      certificate.certificate = "CERTIFICATE"
+      certificate.key = 'KEY'
+      certificate.certificate = 'CERTIFICATE'
       expect(redis).to receive(:set).with("#{domain}.key", an_instance_of(String))
       expect(redis).to receive(:set).with("#{domain}.crt", an_instance_of(String))
       LetsEncrypt::Redis.save(certificate)
@@ -36,8 +36,8 @@
 
   describe '#delete' do
     it 'deletes certificate from redis' do
-      certificate.key = "KEY"
-      certificate.certificate = "CERTIFICATE"
+      certificate.key = 'KEY'
+      certificate.certificate = 'CERTIFICATE'
       expect(redis).to receive(:del).with("#{domain}.key")
       expect(redis).to receive(:del).with("#{domain}.crt")
       LetsEncrypt::Redis.delete(certificate)
diff --git a/spec/letsencrypt_spec.rb b/spec/letsencrypt_spec.rb
index 4ea5a3f..a4d288a 100644
--- a/spec/letsencrypt_spec.rb
+++ b/spec/letsencrypt_spec.rb
@@ -23,7 +23,7 @@
   end
 
   describe '#register' do
-    let(:acme_client) { double(::Acme::Client) }
+    let(:acme_client) { double(Acme::Client) }
     let(:acme_account) { double }
 
     it 'register new account to Let\'s Encrypt' do
@@ -39,9 +39,9 @@
   end
 
   describe 'certificate_model' do
-    class OtherModel < LetsEncrypt::Certificate
-    end
     before do
+      stub_const('OtherModel', Class.new(LetsEncrypt::Certificate))
+
       LetsEncrypt.config.certificate_model = 'OtherModel'
       allow(LetsEncrypt).to receive(:certificate_model) { LetsEncrypt.config.certificate_model.constantize }
     end
diff --git a/spec/models/lets_encrypt/certificate_spec.rb b/spec/models/lets_encrypt/certificate_spec.rb
index e338e0f..3d17873 100644
--- a/spec/models/lets_encrypt/certificate_spec.rb
+++ b/spec/models/lets_encrypt/certificate_spec.rb
@@ -13,8 +13,7 @@
     LetsEncrypt.config.save_to_redis = false
 
     mock_cert.public_key = key.public_key
-    mock_cert.sign(key, OpenSSL::Digest::SHA256.new)
-
+    mock_cert.sign(key, OpenSSL::Digest.new('SHA256'))
   end
 
   describe '#active?' do
@@ -90,7 +89,7 @@
   describe '#verify' do
     subject(:cert) { LetsEncrypt::Certificate.new(domain: 'example.com') }
 
-    let(:acme_client) { double(::Acme::Client) }
+    let(:acme_client) { double(Acme::Client) }
     let(:acme_order) { double }
     let(:acme_authorization) { double }
     let(:acme_challenge) { double }
@@ -104,12 +103,10 @@
       allow(acme_authorization).to receive(:http).and_return(acme_challenge)
       allow(acme_challenge).to receive(:reload)
 
-      # rubocop:disable Metrics/LineLength
       allow(acme_challenge).to receive(:filename).and_return('.well-known/acme-challenge/path').at_least(1).times
       allow(acme_challenge).to receive(:file_content).and_return('content').at_least(1).times
 
       allow(acme_challenge).to receive(:request_validation).and_return(true).at_least(1).times
-      # rubocop:enable Metrics/LineLength
     end
 
     describe 'when status is valid' do
@@ -118,7 +115,6 @@
       it { is_expected.to have_attributes(verify: true) }
     end
 
-
     describe 'when status is pending to valid' do
       before do
         allow(acme_challenge).to receive(:status).and_return('pending')
@@ -130,7 +126,7 @@
 
     describe 'when Acme::Client::Error is raised' do
       before do
-        allow(acme_challenge).to receive(:status).and_raise(::Acme::Client::Error::BadNonce)
+        allow(acme_challenge).to receive(:status).and_raise(Acme::Client::Error::BadNonce)
         allow(acme_challenge).to receive(:status).and_return('valid')
       end
 
@@ -141,7 +137,7 @@
   describe '#issue' do
     subject(:cert) { LetsEncrypt::Certificate.new(domain: 'example.com', key: key) }
 
-    let(:acme_client) { double(::Acme::Client) }
+    let(:acme_client) { double(Acme::Client) }
     let(:acme_order) { double }
     let(:mock_cert) { OpenSSL::X509::Certificate.new }
 
@@ -151,7 +147,7 @@
       mock_cert.subject = OpenSSL::X509::Name.parse('CN=example.com/C=EE')
       mock_cert.not_before = Time.zone.now
       mock_cert.not_after = 1.month.from_now
-      mock_cert.sign(key, OpenSSL::Digest::SHA256.new)
+      mock_cert.sign(key, OpenSSL::Digest.new('SHA256'))
 
       allow(LetsEncrypt).to receive(:client).and_return(acme_client)
       allow(acme_client).to receive(:new_order).and_return(acme_order)
diff --git a/spec/rails_helper.rb b/spec/rails_helper.rb
index 3d4f397..c1f57bb 100644
--- a/spec/rails_helper.rb
+++ b/spec/rails_helper.rb
@@ -3,9 +3,9 @@
 # This file is copied to spec/ when you run 'rails generate rspec:install'
 require 'spec_helper'
 ENV['RAILS_ENV'] ||= 'test'
-require File.expand_path('../dummy/config/environment', __FILE__)
+require File.expand_path('dummy/config/environment', __dir__)
 # Prevent database truncation if the environment is production
-abort("The Rails environment is running in production mode!") if Rails.env.production?
+abort('The Rails environment is running in production mode!') if Rails.env.production?
 require 'rspec/rails'
 # Add additional requires below this line. Rails is not loaded until this point!
 
@@ -22,19 +22,16 @@
 # directory. Alternatively, in the individual `*_spec.rb` files, manually
 # require only the support files necessary.
 #
-Dir[File.expand_path("../../spec/support/**/*.rb", __FILE__)].each { |f| require f }
-
-# rubocop:disable Metrics/LineLength
-ActiveRecord::Migrator.migrations_paths = [File.expand_path("../../spec/dummy/db/migrate", __FILE__)]
-# rubocop:enable Metrics/LineLength
+Dir[File.expand_path('../spec/support/**/*.rb', __dir__)].sort.each { |f| require f }
 
+ActiveRecord::Migrator.migrations_paths = [File.expand_path('../spec/dummy/db/migrate', __dir__)]
 # Checks for pending migrations before tests are run.
 # If you are not using ActiveRecord, you can remove this line.
 ActiveRecord::Migration.maintain_test_schema!
 
 RSpec.configure do |config|
   # Remove this line if you're not using ActiveRecord or ActiveRecord fixtures
-  config.fixture_path = "#{::Rails.root}/spec/fixtures"
+  config.fixture_path = Rails.root.join('spec/fixtures').to_s
 
   # If you're not using ActiveRecord, or you'd prefer not to run each of your
   # examples within a transaction, remove the following line or assign false
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index c88b77a..f8a6674 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -21,7 +21,7 @@
 SimpleCov.start do
   formatter SimpleCov::Formatter::MultiFormatter.new(
     [
-      SimpleCov::Formatter::HTMLFormatter,
+      SimpleCov::Formatter::HTMLFormatter
     ]
   )
 
@@ -69,53 +69,51 @@
   # triggering implicit auto-inclusion in groups with matching metadata.
   config.shared_context_metadata_behavior = :apply_to_host_groups
 
-# The settings below are suggested to provide a good initial experience
-# with RSpec, but feel free to customize to your heart's content.
-=begin
-  # This allows you to limit a spec run to individual examples or groups
-  # you care about by tagging them with `:focus` metadata. When nothing
-  # is tagged with `:focus`, all examples get run. RSpec also provides
-  # aliases for `it`, `describe`, and `context` that include `:focus`
-  # metadata: `fit`, `fdescribe` and `fcontext`, respectively.
-  config.filter_run_when_matching :focus
-
-  # Allows RSpec to persist some state between runs in order to support
-  # the `--only-failures` and `--next-failure` CLI options. We recommend
-  # you configure your source control system to ignore this file.
-  config.example_status_persistence_file_path = 'spec/examples.txt'
-
-  # Limits the available syntax to the non-monkey patched syntax that is
-  # recommended. For more details, see:
-  #   - http://rspec.info/blog/2012/06/rspecs-new-expectation-syntax/
-  #   - http://www.teaisaweso.me/blog/2013/05/27/rspecs-new-message-expectation-syntax/
-  #   - http://rspec.info/blog/2014/05/notable-changes-in-rspec-3/#zero-monkey-patching-mode
-  config.disable_monkey_patching!
-
-  # Many RSpec users commonly either run the entire suite or an individual
-  # file, and it's useful to allow more verbose output when running an
-  # individual spec file.
-  if config.files_to_run.one?
-    # Use the documentation formatter for detailed output,
-    # unless a formatter has already been configured
-    # (e.g. via a command-line flag).
-    config.default_formatter = 'doc'
-  end
-
-  # Print the 10 slowest examples and example groups at the
-  # end of the spec run, to help surface which specs are running
-  # particularly slow.
-  config.profile_examples = 10
-
-  # Run specs in random order to surface order dependencies. If you find an
-  # order dependency and want to debug it, you can fix the order by providing
-  # the seed, which is printed after each run.
-  #     --seed 1234
-  config.order = :random
-
-  # Seed global randomization in this process using the `--seed` CLI option.
-  # Setting this allows you to use `--seed` to deterministically reproduce
-  # test failures related to randomization by passing the same `--seed` value
-  # as the one that triggered the failure.
-  Kernel.srand config.seed
-=end
+  # The settings below are suggested to provide a good initial experience
+  # with RSpec, but feel free to customize to your heart's content.
+  #   # This allows you to limit a spec run to individual examples or groups
+  #   # you care about by tagging them with `:focus` metadata. When nothing
+  #   # is tagged with `:focus`, all examples get run. RSpec also provides
+  #   # aliases for `it`, `describe`, and `context` that include `:focus`
+  #   # metadata: `fit`, `fdescribe` and `fcontext`, respectively.
+  #   config.filter_run_when_matching :focus
+  #
+  #   # Allows RSpec to persist some state between runs in order to support
+  #   # the `--only-failures` and `--next-failure` CLI options. We recommend
+  #   # you configure your source control system to ignore this file.
+  #   config.example_status_persistence_file_path = 'spec/examples.txt'
+  #
+  #   # Limits the available syntax to the non-monkey patched syntax that is
+  #   # recommended. For more details, see:
+  #   #   - http://rspec.info/blog/2012/06/rspecs-new-expectation-syntax/
+  #   #   - http://www.teaisaweso.me/blog/2013/05/27/rspecs-new-message-expectation-syntax/
+  #   #   - http://rspec.info/blog/2014/05/notable-changes-in-rspec-3/#zero-monkey-patching-mode
+  #   config.disable_monkey_patching!
+  #
+  #   # Many RSpec users commonly either run the entire suite or an individual
+  #   # file, and it's useful to allow more verbose output when running an
+  #   # individual spec file.
+  #   if config.files_to_run.one?
+  #     # Use the documentation formatter for detailed output,
+  #     # unless a formatter has already been configured
+  #     # (e.g. via a command-line flag).
+  #     config.default_formatter = 'doc'
+  #   end
+  #
+  #   # Print the 10 slowest examples and example groups at the
+  #   # end of the spec run, to help surface which specs are running
+  #   # particularly slow.
+  #   config.profile_examples = 10
+  #
+  #   # Run specs in random order to surface order dependencies. If you find an
+  #   # order dependency and want to debug it, you can fix the order by providing
+  #   # the seed, which is printed after each run.
+  #   #     --seed 1234
+  #   config.order = :random
+  #
+  #   # Seed global randomization in this process using the `--seed` CLI option.
+  #   # Setting this allows you to use `--seed` to deterministically reproduce
+  #   # test failures related to randomization by passing the same `--seed` value
+  #   # as the one that triggered the failure.
+  #   Kernel.srand config.seed
 end