diff --git a/.rubocop.yml b/.rubocop.yml
index 2f96046..c38df9f 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -22,3 +22,6 @@ RSpec/FilePath:
 RSpec/SpecFilePathFormat:
   CustomTransform:
     OmniAuth: omniauth
+
+Style/NumericPredicate:
+  Enabled: false
diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
index bcdd4b9..3e8096d 100644
--- a/.rubocop_todo.yml
+++ b/.rubocop_todo.yml
@@ -11,11 +11,6 @@ Lint/EnsureReturn:
   Exclude:
     - 'lib/omniauth/strategies/cas/logout_request.rb'
 
-# This cop supports unsafe autocorrection (--autocorrect-all).
-Lint/UselessAssignment:
-  Exclude:
-    - 'lib/omniauth/strategies/cas.rb'
-
 Lint/UselessRescue:
   Exclude:
     - 'lib/omniauth/strategies/cas/logout_request.rb'
@@ -48,10 +43,6 @@ Naming/AccessorMethodName:
   Exclude:
     - 'lib/omniauth/strategies/cas/service_ticket_validator.rb'
 
-Naming/ConstantName:
-  Exclude:
-    - 'lib/omniauth/strategies/cas.rb'
-
 # Configuration parameters: ExpectMatchingDefinition, CheckDefinitionPathHierarchy, CheckDefinitionPathHierarchyRoots, Regex, IgnoreExecutableScripts, AllowedAcronyms.
 # CheckDefinitionPathHierarchyRoots: lib, spec, test, src
 # 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
@@ -122,49 +113,6 @@ Style/Documentation:
     - 'lib/omniauth/strategies/cas/logout_request.rb'
     - 'lib/omniauth/strategies/cas/service_ticket_validator.rb'
 
-# This cop supports unsafe autocorrection (--autocorrect-all).
-# Configuration parameters: EnforcedStyle.
-# SupportedStyles: always, always_true, never
-Style/FrozenStringLiteralComment:
-  Exclude:
-    - 'lib/omniauth-cas.rb'
-    - 'lib/omniauth/cas.rb'
-    - 'lib/omniauth/cas/version.rb'
-    - 'lib/omniauth/strategies/cas.rb'
-    - 'lib/omniauth/strategies/cas/logout_request.rb'
-    - 'lib/omniauth/strategies/cas/service_ticket_validator.rb'
-
-# This cop supports unsafe autocorrection (--autocorrect-all).
-# Configuration parameters: AllowedReceivers.
-# AllowedReceivers: Thread.current
-Style/HashEachMethods:
-  Exclude:
-    - 'lib/omniauth/strategies/cas.rb'
-
-# This cop supports unsafe autocorrection (--autocorrect-all).
-# Configuration parameters: EnforcedStyle.
-# SupportedStyles: literals, strict
-Style/MutableConstant:
-  Exclude:
-    - 'lib/omniauth/cas/version.rb'
-    - 'lib/omniauth/strategies/cas.rb'
-    - 'lib/omniauth/strategies/cas/service_ticket_validator.rb'
-
-# This cop supports unsafe autocorrection (--autocorrect-all).
-# Configuration parameters: EnforcedStyle, AllowedMethods, AllowedPatterns.
-# SupportedStyles: predicate, comparison
-Style/NumericPredicate:
-  Exclude:
-    - 'spec/**/*'
-    - 'lib/omniauth/strategies/cas/service_ticket_validator.rb'
-
-# This cop supports unsafe autocorrection (--autocorrect-all).
-# Configuration parameters: EnforcedStyle.
-# SupportedStyles: short, verbose
-Style/PreferredHashMethods:
-  Exclude:
-    - 'lib/omniauth/strategies/cas.rb'
-
 # This cop supports safe autocorrection (--autocorrect).
 # Configuration parameters: AllowHeredoc, AllowURI, URISchemes, IgnoreCopDirectives, AllowedPatterns.
 # URISchemes: http, https
diff --git a/lib/omniauth-cas.rb b/lib/omniauth-cas.rb
index 3de039d..a98c23d 100644
--- a/lib/omniauth-cas.rb
+++ b/lib/omniauth-cas.rb
@@ -1 +1,3 @@
+# frozen_string_literal: true
+
 require 'omniauth/cas'
diff --git a/lib/omniauth/cas.rb b/lib/omniauth/cas.rb
index 2fe34bb..5990130 100644
--- a/lib/omniauth/cas.rb
+++ b/lib/omniauth/cas.rb
@@ -1,2 +1,4 @@
+# frozen_string_literal: true
+
 require 'omniauth/cas/version'
 require 'omniauth/strategies/cas'
diff --git a/lib/omniauth/cas/version.rb b/lib/omniauth/cas/version.rb
index 0fb6fc5..160d8e1 100644
--- a/lib/omniauth/cas/version.rb
+++ b/lib/omniauth/cas/version.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module OmniAuth
   module Cas
     VERSION = '3.0.0'
diff --git a/lib/omniauth/strategies/cas.rb b/lib/omniauth/strategies/cas.rb
index e1db34a..77868ac 100644
--- a/lib/omniauth/strategies/cas.rb
+++ b/lib/omniauth/strategies/cas.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'omniauth'
 require 'addressable/uri'
 
@@ -48,7 +50,7 @@ class InvalidCASTicket < StandardError; end
       option :phone_key, 'phone'
 
       # As required by https://github.com/intridea/omniauth/wiki/Auth-Hash-Schema
-      AuthHashSchemaKeys = %w[name email nickname first_name last_name location image phone]
+      AUTH_HASH_SCHEMA_KEYS = %w[name email nickname first_name last_name location image phone].freeze
       info do
         prune!({
                  name: raw_info[options[:name_key].to_s],
@@ -64,7 +66,7 @@ class InvalidCASTicket < StandardError; end
 
       extra do
         prune!(
-          raw_info.delete_if { |k, _v| AuthHashSchemaKeys.include?(k) }
+          raw_info.delete_if { |k, _v| AUTH_HASH_SCHEMA_KEYS.include?(k) }
         )
       end
 
@@ -104,7 +106,7 @@ def request_phase
       end
 
       def on_sso_path?
-        request.post? && request.params.has_key?('logoutRequest')
+        request.post? && request.params.key?('logoutRequest')
       end
 
       def single_sign_out_phase
@@ -177,7 +179,7 @@ def login_url(service)
       #
       # @return [String] the new joined URL.
       def append_params(base, params)
-        params = params.each { |_k, v| v = Rack::Utils.escape(v) }
+        params = params.each_value { |v| Rack::Utils.escape(v) }
         Addressable::URI.parse(base).tap do |base_uri|
           base_uri.query_values = (base_uri.query_values || {}).merge(params)
         end.to_s
diff --git a/lib/omniauth/strategies/cas/logout_request.rb b/lib/omniauth/strategies/cas/logout_request.rb
index 3448208..0a33cdc 100644
--- a/lib/omniauth/strategies/cas/logout_request.rb
+++ b/lib/omniauth/strategies/cas/logout_request.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module OmniAuth
   module Strategies
     class CAS
diff --git a/lib/omniauth/strategies/cas/service_ticket_validator.rb b/lib/omniauth/strategies/cas/service_ticket_validator.rb
index 6b813fa..9db770b 100644
--- a/lib/omniauth/strategies/cas/service_ticket_validator.rb
+++ b/lib/omniauth/strategies/cas/service_ticket_validator.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'net/http'
 require 'net/https'
 require 'nokogiri'
@@ -6,7 +8,7 @@ module OmniAuth
   module Strategies
     class CAS
       class ServiceTicketValidator
-        VALIDATION_REQUEST_HEADERS = { 'Accept' => '*/*' }
+        VALIDATION_REQUEST_HEADERS = { 'Accept' => '*/*' }.freeze
 
         attr_reader :success_body