diff --git a/.rubocop.yml b/.rubocop.yml
index fe3bc03..c84a565 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -8,13 +8,17 @@ AllCops:
     - "Rakefile"
     - "yard/**/*"
     - "website/**/*"
+Metrics/AbcSize:
+  Enabled: false
 Metrics/ClassLength:
-  Exclude:
-    - "lib/signet/oauth_1/client.rb"
-    - "lib/signet/oauth_1/server.rb"
-    - "lib/signet/oauth_2/client.rb"
+  Enabled: false
+Metrics/CyclomaticComplexity:
+  Max: 30
+Metrics/MethodLength:
+  Enabled: false
 Metrics/ModuleLength:
-  Exclude:
-    - "lib/signet/oauth_1.rb"
+  Enabled: false
+Metrics/PerceivedComplexity:
+  Max: 30
 Style/Documentation:
   Enabled: false
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 647435f..9a6357c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,11 +1,8 @@
 # Release History
 
-## [0.14.1](https://www.github.com/googleapis/signet/compare/v0.14.0...v0.14.1) (2021-01-27)
+## 0.14.1 / 2021-01-27
 
-
-### Bug Fixes
-
-* Fix OAuth1 signature with duplicate query param names ([9f5b81a](https://www.github.com/googleapis/signet/commit/9f5b81a60625a6e6f0e5bca24c67b90e73d7479b))
+* Fix OAuth1 signature with duplicate query param names
 
 ## 0.14.0 / 2020-03-31
 
diff --git a/README.md b/README.md
index f3e5fda..c9f851c 100644
--- a/README.md
+++ b/README.md
@@ -31,8 +31,8 @@ require 'signet/oauth_2/client'
 client = Signet::OAuth2::Client.new(
   :authorization_uri => 'https://accounts.google.com/o/oauth2/auth',
   :token_credential_uri =>  'https://oauth2.googleapis.com/token',
-  :client_id => '44410190108-74nkm6jc5e3vvjqis803frkvmu88cu3a.apps.googleusercontent.com',
-  :client_secret => 'X1NUhvO-rQr9sm8uUSMY8i7v',
+  :client_id => "#{YOUR_CLIENT_ID}.apps.googleusercontent.com",
+  :client_secret => YOUR_CLIENT_SECRET,
   :scope => 'email profile',
   :redirect_uri => 'https://example.client.com/oauth'
 )
@@ -59,8 +59,11 @@ Be sure `https://rubygems.org` is in your gem sources.
 
 ## Supported Ruby Versions
 
-This library requires Ruby 2.4 or later.
-In general, this library supports Ruby versions that are considered current and
-supported by Ruby Core (that is, Ruby versions that are either in normal
-maintenance or in security maintenance).
-See https://www.ruby-lang.org/en/downloads/branches/ for further details.
+This library is supported on Ruby 2.5+.
+
+Google provides official support for Ruby versions that are actively supported
+by Ruby Core—that is, Ruby versions that are either in normal maintenance or in
+security maintenance, and not end of life. Currently, this means Ruby 2.5 and
+later. Older versions of Ruby _may_ still work, but are unsupported and not
+recommended. See https://www.ruby-lang.org/en/downloads/branches/ for details
+about the Ruby support schedule.
diff --git a/lib/signet.rb b/lib/signet.rb
index 77c0d0e..b3462a8 100644
--- a/lib/signet.rb
+++ b/lib/signet.rb
@@ -15,8 +15,6 @@
 require "signet/version"
 
 module Signet #:nodoc:
-  # rubocop:disable Metrics/AbcSize
-  # rubocop:disable Metrics/MethodLength
   def self.parse_auth_param_list auth_param_string
     # Production rules from:
     # http://tools.ietf.org/html/draft-ietf-httpbis-p1-messaging-12
@@ -54,11 +52,12 @@ def self.parse_auth_param_list auth_param_string
     # Now parse the auth-param pair strings & turn them into key-value pairs.
     (auth_param_pairs.each_with_object [] do |pair, accu|
       name, value = pair.split "=", 2
-      if value =~ /^".*"$/
+      case value
+      when /^".*"$/
         value = value.gsub(/^"(.*)"$/, '\1').gsub(/\\(.)/, '\1')
-      elsif value =~ /^'.*'$/
+      when /^'.*'$/
         value = value.gsub(/^'(.*)'$/, '\1').gsub(/\\(.)/, '\1')
-      elsif value =~ %r{[\(\)<>@,;:\\\"/\[\]?={}]}
+      when %r{[()<>@,;:\\"/\[\]?={}]}
         # Certain special characters are not allowed
         raise ParseError,
               "Unexpected characters in auth param " \
@@ -68,6 +67,4 @@ def self.parse_auth_param_list auth_param_string
       accu << [name, value]
     end)
   end
-  # rubocop:enable Metrics/AbcSize
-  # rubocop:enable Metrics/MethodLength
 end
diff --git a/lib/signet/oauth_1.rb b/lib/signet/oauth_1.rb
index f267b9e..018e99b 100644
--- a/lib/signet/oauth_1.rb
+++ b/lib/signet/oauth_1.rb
@@ -49,9 +49,8 @@ def self.generate_timestamp
     #
     # @return [String] A random nonce.
     def self.generate_nonce
-      SecureRandom.random_bytes(16).unpack("H*").join ""
+      SecureRandom.random_bytes(16).unpack("H*").join
     end
-    # rubocop:disable Metrics/MethodLength
 
     ##
     # Processes an options <code>Hash</code> to find a credential key value.
@@ -65,7 +64,7 @@ def self.generate_nonce
     # @return [String] The credential key value.
     def self.extract_credential_key_option credential_type, options
       # Normalize key to String to allow indifferent access.
-      options = options.each_with_object({}) { |(k, v), accu| accu[k.to_s] = v; }
+      options = options.to_h.transform_keys(&:to_s)
       credential_key = "#{credential_type}_credential_key"
       credential = "#{credential_type}_credential"
       if options[credential_key]
@@ -107,7 +106,7 @@ def self.extract_credential_key_option credential_type, options
     # @return [String] The credential secret value.
     def self.extract_credential_secret_option credential_type, options
       # Normalize key to String to allow indifferent access.
-      options = options.each_with_object({}) { |(k, v), accu| accu[k.to_s] = v; }
+      options = options.to_h.transform_keys(&:to_s)
       credential_secret = "#{credential_type}_credential_secret"
       credential = "#{credential_type}_credential"
       if options[credential_secret]
@@ -136,7 +135,6 @@ def self.extract_credential_secret_option credential_type, options
       end
       credential_secret
     end
-    # rubocop:enable Metrics/MethodLength
 
     ##
     # Normalizes a set of OAuth parameters according to the algorithm given
@@ -214,7 +212,7 @@ def self.generate_authorization_header parameters, realm = nil
         realm = realm.gsub '"', '\"'
         parameter_list.unshift "realm=\"#{realm}\""
       end
-      "OAuth " + parameter_list.join(", ")
+      "OAuth #{parameter_list.join ', '}"
     end
 
     ##
@@ -228,7 +226,7 @@ def self.parse_authorization_header field_value
       when /^OAuth$/i
         # Other token types may be supported eventually
         pairs = Signet.parse_auth_param_list(field_value[/^OAuth\s+(.*)$/i, 1])
-        return (pairs.each_with_object [] do |(k, v), accu|
+        (pairs.each_with_object [] do |(k, v), accu|
           if k != "realm"
             k = unencode k
             v = unencode v
@@ -274,24 +272,18 @@ def self.sign_parameters method, uri, parameters,
       # be a temporary credential secret when obtaining a token credential
       # for the first time
       base_string = generate_base_string method, uri, parameters
-      parameters = parameters.each_with_object({}) { |(k, v), h| h[k.to_s] = v; }
+      parameters = parameters.to_h.transform_keys(&:to_s)
       signature_method = parameters["oauth_signature_method"]
       case signature_method
       when "HMAC-SHA1"
         require "signet/oauth_1/signature_methods/hmac_sha1"
-        return Signet::OAuth1::HMACSHA1.generate_signature(
-          base_string, client_credential_secret, token_credential_secret
-        )
+        Signet::OAuth1::HMACSHA1.generate_signature base_string, client_credential_secret, token_credential_secret
       when "RSA-SHA1"
         require "signet/oauth_1/signature_methods/rsa_sha1"
-        return Signet::OAuth1::RSASHA1.generate_signature(
-          base_string, client_credential_secret, token_credential_secret
-        )
+        Signet::OAuth1::RSASHA1.generate_signature base_string, client_credential_secret, token_credential_secret
       when "PLAINTEXT"
         require "signet/oauth_1/signature_methods/plaintext"
-        return Signet::OAuth1::PLAINTEXT.generate_signature(
-          base_string, client_credential_secret, token_credential_secret
-        )
+        Signet::OAuth1::PLAINTEXT.generate_signature base_string, client_credential_secret, token_credential_secret
       else
         raise NotImplementedError,
               "Unsupported signature method: #{signature_method}"
@@ -396,7 +388,7 @@ def self.unsigned_token_credential_parameters options = {}
       raise ArgumentError, "Missing :client_credential_key parameter." if client_credential_key.nil?
       raise ArgumentError, "Missing :temporary_credential_key parameter." if temporary_credential_key.nil?
       raise ArgumentError, "Missing :verifier parameter." if options[:verifier].nil?
-      parameters = [
+      [
         ["oauth_consumer_key", client_credential_key],
         ["oauth_token", temporary_credential_key],
         ["oauth_signature_method", options[:signature_method]],
@@ -405,8 +397,6 @@ def self.unsigned_token_credential_parameters options = {}
         ["oauth_verifier", options[:verifier]],
         ["oauth_version", "1.0"]
       ]
-      # No additional parameters allowed here
-      parameters
     end
 
     ##
diff --git a/lib/signet/oauth_1/client.rb b/lib/signet/oauth_1/client.rb
index 7956a27..ce25935 100644
--- a/lib/signet/oauth_1/client.rb
+++ b/lib/signet/oauth_1/client.rb
@@ -89,7 +89,7 @@ def initialize options = {}
       # @see Signet::OAuth1::Client#initialize
       def update! options = {}
         # Normalize key to String to allow indifferent access.
-        options = options.each_with_object({}) { |(k, v), accu| accu[k.to_s] = v; }
+        options = options.to_h.transform_keys(&:to_s)
         self.temporary_credential_uri = options["temporary_credential_uri"]
         self.authorization_uri = options["authorization_uri"]
         self.token_credential_uri = options["token_credential_uri"]
@@ -128,12 +128,12 @@ def temporary_credential_uri
       #   new_temporary_credential_uri
       #   The temporary credentials URI.
       def temporary_credential_uri= new_temporary_credential_uri
-        if !new_temporary_credential_uri.nil?
+        if new_temporary_credential_uri.nil?
+          @temporary_credential_uri = nil
+        else
           new_temporary_credential_uri =
             Addressable::URI.parse new_temporary_credential_uri
           @temporary_credential_uri = new_temporary_credential_uri
-        else
-          @temporary_credential_uri = nil
         end
       end
       alias request_token_uri= temporary_credential_uri=
@@ -163,14 +163,14 @@ def authorization_uri options = {}
       # @param [Addressable::URI, String, #to_str] new_authorization_uri
       #   The authorization URI.
       def authorization_uri= new_authorization_uri
-        if !new_authorization_uri.nil?
+        if new_authorization_uri.nil?
+          @authorization_uri = nil
+        else
           new_authorization_uri = Addressable::URI.send(
             new_authorization_uri.is_a?(Hash) ? :new : :parse,
             new_authorization_uri
           )
           @authorization_uri = new_authorization_uri
-        else
-          @authorization_uri = nil
         end
       end
 
@@ -189,14 +189,14 @@ def token_credential_uri
       # @param [Addressable::URI, Hash, String, #to_str] new_token_credential_uri
       #   The token credential URI.
       def token_credential_uri= new_token_credential_uri
-        if !new_token_credential_uri.nil?
+        if new_token_credential_uri.nil?
+          @token_credential_uri = nil
+        else
           new_token_credential_uri = Addressable::URI.send(
             new_token_credential_uri.is_a?(Hash) ? :new : :parse,
             new_token_credential_uri
           )
           @token_credential_uri = new_token_credential_uri
-        else
-          @token_credential_uri = nil
         end
       end
       alias access_token_uri= token_credential_uri=
@@ -217,8 +217,7 @@ def client_credential
         elsif !client_credential_key && !client_credential_secret
           nil
         else
-          raise ArgumentError,
-                "The client credential key and secret must be set."
+          raise ArgumentError, "The client credential key and secret must be set."
         end
       end
       alias consumer_token client_credential
@@ -229,7 +228,10 @@ def client_credential
       # @param [Signet::OAuth1::Credential] new_client_credential
       #   The client credentials.
       def client_credential= new_client_credential
-        if !new_client_credential.nil?
+        if new_client_credential.nil?
+          @client_credential_key = nil
+          @client_credential_secret = nil
+        else
           unless new_client_credential.is_a? ::Signet::OAuth1::Credential
             raise TypeError,
                   "Expected Signet::OAuth1::Credential, " \
@@ -237,9 +239,6 @@ def client_credential= new_client_credential
           end
           @client_credential_key = new_client_credential.key
           @client_credential_secret = new_client_credential.secret
-        else
-          @client_credential_key = nil
-          @client_credential_secret = nil
         end
       end
       alias consumer_token= client_credential=
@@ -259,15 +258,15 @@ def client_credential_key
       # @param [String, #to_str] new_client_credential_key
       #   The client credential key.
       def client_credential_key= new_client_credential_key
-        if !new_client_credential_key.nil?
+        if new_client_credential_key.nil?
+          @client_credential_key = nil
+        else
           unless new_client_credential_key.respond_to? :to_str
             raise TypeError,
                   "Can't convert #{new_client_credential_key.class} into String."
           end
           new_client_credential_key = new_client_credential_key.to_str
           @client_credential_key = new_client_credential_key
-        else
-          @client_credential_key = nil
         end
       end
       alias consumer_key= client_credential_key=
@@ -287,7 +286,9 @@ def client_credential_secret
       # @param [String, #to_str] new_client_credential_secret
       #   The client credential secret.
       def client_credential_secret= new_client_credential_secret
-        if !new_client_credential_secret.nil?
+        if new_client_credential_secret.nil?
+          @client_credential_secret = nil
+        else
           unless new_client_credential_secret.respond_to? :to_str
             raise TypeError,
                   "Can't convert #{new_client_credential_secret.class} " \
@@ -295,8 +296,6 @@ def client_credential_secret= new_client_credential_secret
           end
           new_client_credential_secret = new_client_credential_secret.to_str
           @client_credential_secret = new_client_credential_secret
-        else
-          @client_credential_secret = nil
         end
       end
       alias consumer_secret= client_credential_secret=
@@ -311,12 +310,10 @@ def temporary_credential
             temporary_credential_key,
             temporary_credential_secret
           )
-        elsif !temporary_credential_key &&
-              !temporary_credential_secret
+        elsif !temporary_credential_key && !temporary_credential_secret
           nil
         else
-          raise ArgumentError,
-                "The temporary credential key and secret must be set."
+          raise ArgumentError, "The temporary credential key and secret must be set."
         end
       end
       alias request_token temporary_credential
@@ -327,7 +324,10 @@ def temporary_credential
       # @param [Signet::OAuth1::Credential] new_temporary_credential
       #   The temporary credentials.
       def temporary_credential= new_temporary_credential
-        if !new_temporary_credential.nil?
+        if new_temporary_credential.nil?
+          @temporary_credential_key = nil
+          @temporary_credential_secret = nil
+        else
           unless new_temporary_credential.is_a? ::Signet::OAuth1::Credential
             raise TypeError,
                   "Expected Signet::OAuth1::Credential, " \
@@ -335,9 +335,6 @@ def temporary_credential= new_temporary_credential
           end
           @temporary_credential_key = new_temporary_credential.key
           @temporary_credential_secret = new_temporary_credential.secret
-        else
-          @temporary_credential_key = nil
-          @temporary_credential_secret = nil
         end
       end
       alias request_token= temporary_credential=
@@ -357,7 +354,9 @@ def temporary_credential_key
       # @param [String, #to_str] new_temporary_credential_key
       #   The temporary credential key.
       def temporary_credential_key= new_temporary_credential_key
-        if !new_temporary_credential_key.nil?
+        if new_temporary_credential_key.nil?
+          @temporary_credential_key = nil
+        else
           unless new_temporary_credential_key.respond_to? :to_str
             raise TypeError,
                   "Can't convert #{new_temporary_credential_key.class} " \
@@ -365,8 +364,6 @@ def temporary_credential_key= new_temporary_credential_key
           end
           new_temporary_credential_key = new_temporary_credential_key.to_str
           @temporary_credential_key = new_temporary_credential_key
-        else
-          @temporary_credential_key = nil
         end
       end
       alias request_token_key= temporary_credential_key=
@@ -386,7 +383,9 @@ def temporary_credential_secret
       # @param [String, #to_str] new_temporary_credential_secret
       #   The temporary credential secret.
       def temporary_credential_secret= new_temporary_credential_secret
-        if !new_temporary_credential_secret.nil?
+        if new_temporary_credential_secret.nil?
+          @temporary_credential_secret = nil
+        else
           unless new_temporary_credential_secret.respond_to? :to_str
             raise TypeError,
                   "Can't convert #{new_temporary_credential_secret.class} " \
@@ -395,8 +394,6 @@ def temporary_credential_secret= new_temporary_credential_secret
           new_temporary_credential_secret =
             new_temporary_credential_secret.to_str
           @temporary_credential_secret = new_temporary_credential_secret
-        else
-          @temporary_credential_secret = nil
         end
       end
       alias request_token_secret= temporary_credential_secret=
@@ -411,12 +408,10 @@ def token_credential
             token_credential_key,
             token_credential_secret
           )
-        elsif !token_credential_key &&
-              !token_credential_secret
+        elsif !token_credential_key && !token_credential_secret
           nil
         else
-          raise ArgumentError,
-                "The token credential key and secret must be set."
+          raise ArgumentError, "The token credential key and secret must be set."
         end
       end
       alias access_token token_credential
@@ -427,7 +422,10 @@ def token_credential
       # @param [Signet::OAuth1::Credential] new_token_credential
       #   The token credentials.
       def token_credential= new_token_credential
-        if !new_token_credential.nil?
+        if new_token_credential.nil?
+          @token_credential_key = nil
+          @token_credential_secret = nil
+        else
           unless new_token_credential.is_a? ::Signet::OAuth1::Credential
             raise TypeError,
                   "Expected Signet::OAuth1::Credential, " \
@@ -435,9 +433,6 @@ def token_credential= new_token_credential
           end
           @token_credential_key = new_token_credential.key
           @token_credential_secret = new_token_credential.secret
-        else
-          @token_credential_key = nil
-          @token_credential_secret = nil
         end
       end
       alias access_token= token_credential=
@@ -457,7 +452,9 @@ def token_credential_key
       # @param [String, #to_str] new_token_credential_key
       #   The token credential key.
       def token_credential_key= new_token_credential_key
-        if !new_token_credential_key.nil?
+        if new_token_credential_key.nil?
+          @token_credential_key = nil
+        else
           unless new_token_credential_key.respond_to? :to_str
             raise TypeError,
                   "Can't convert #{new_token_credential_key.class} " \
@@ -465,8 +462,6 @@ def token_credential_key= new_token_credential_key
           end
           new_token_credential_key = new_token_credential_key.to_str
           @token_credential_key = new_token_credential_key
-        else
-          @token_credential_key = nil
         end
       end
       alias access_token_key= token_credential_key=
@@ -486,7 +481,9 @@ def token_credential_secret
       # @param [String, #to_str] new_token_credential_secret
       #   The token credential secret.
       def token_credential_secret= new_token_credential_secret
-        if !new_token_credential_secret.nil?
+        if new_token_credential_secret.nil?
+          @token_credential_secret = nil
+        else
           unless new_token_credential_secret.respond_to? :to_str
             raise TypeError,
                   "Can't convert #{new_token_credential_secret.class} " \
@@ -495,8 +492,6 @@ def token_credential_secret= new_token_credential_secret
           new_token_credential_secret =
             new_token_credential_secret.to_str
           @token_credential_secret = new_token_credential_secret
-        else
-          @token_credential_secret = nil
         end
       end
       alias access_token_secret= token_credential_secret=
@@ -515,15 +510,15 @@ def callback
       # @param [String, #to_str] new_callback
       #   The OAuth callback.
       def callback= new_callback
-        if !new_callback.nil?
+        if new_callback.nil?
+          @callback = nil
+        else
           unless new_callback.respond_to? :to_str
             raise TypeError,
                   "Can't convert #{new_callback.class} into String."
           end
           new_callback = new_callback.to_str
           @callback = new_callback
-        else
-          @callback = nil
         end
       end
 
@@ -556,7 +551,7 @@ def two_legged= new_two_legged
       # @note A serialized client contains sensitive information. Persist or transmit with care.
       #
       # @return [String] A serialized JSON representation of the client.
-      def to_json
+      def to_json *_args
         MultiJson.dump(
           "temporary_credential_uri"    => temporary_credential_uri,
           "authorization_uri"           => authorization_uri,
@@ -571,8 +566,6 @@ def to_json
           "token_credential_secret"     => token_credential_secret
         )
       end
-      # rubocop:disable Metrics/AbcSize
-      # rubocop:disable Metrics/MethodLength
 
       ##
       # Generates a request for temporary credentials.
@@ -635,8 +628,6 @@ def generate_temporary_credential_request options = {}
           req.headers = Faraday::Utils::Headers.new headers
         end
       end
-      # rubocop:enable Metrics/AbcSize
-      # rubocop:enable Metrics/MethodLength
       alias generate_request_token_request generate_temporary_credential_request
 
       ##
@@ -709,8 +700,6 @@ def fetch_temporary_credential! options = {}
         self.temporary_credential = credential
       end
       alias fetch_request_token! fetch_temporary_credential!
-      # rubocop:disable Metrics/AbcSize
-      # rubocop:disable Metrics/MethodLength
 
       ##
       # Generates a request for token credentials.
@@ -776,7 +765,6 @@ def generate_token_credential_request options = {}
           req.headers = Faraday::Utils::Headers.new headers
         end
       end
-      # rubocop:enable Metrics/MethodLength
       alias generate_access_token_request generate_token_credential_request
 
       ##
@@ -818,7 +806,6 @@ def fetch_token_credential options = {}
           message, request: request, response: response
         )
       end
-      # rubocop:enable Metrics/AbcSize
       alias fetch_access_token fetch_token_credential
 
       ##
@@ -846,10 +833,6 @@ def fetch_token_credential! options = {}
         self.token_credential = credential
       end
       alias fetch_access_token! fetch_token_credential!
-      # rubocop:disable Metrics/AbcSize
-      # rubocop:disable Metrics/CyclomaticComplexity
-      # rubocop:disable Metrics/MethodLength
-      # rubocop:disable Metrics/PerceivedComplexity
 
       ##
       # Generates an authenticated request for protected resources.
@@ -950,7 +933,7 @@ def generate_authenticated_request options = {}
           request.body = env[:body]
 
           post_parameters = Addressable::URI.form_unencode env[:body]
-          parameters = parameters.concat post_parameters
+          parameters.concat post_parameters
         end
 
         # No need to attach URI query parameters, the .sign_parameters
@@ -970,10 +953,6 @@ def generate_authenticated_request options = {}
         request["Cache-Control"] = "no-store"
         request
       end
-      # rubocop:enable Metrics/AbcSize
-      # rubocop:enable Metrics/CyclomaticComplexity
-      # rubocop:enable Metrics/MethodLength
-      # rubocop:enable Metrics/PerceivedComplexity
 
       ##
       # Transmits a request for a protected resource.
diff --git a/lib/signet/oauth_1/credential.rb b/lib/signet/oauth_1/credential.rb
index b3a4ec5..c02fe9c 100644
--- a/lib/signet/oauth_1/credential.rb
+++ b/lib/signet/oauth_1/credential.rb
@@ -15,11 +15,6 @@
 module Signet #:nodoc:
   module OAuth1
     class Credential
-      # rubocop:disable Metrics/AbcSize
-      # rubocop:disable Metrics/CyclomaticComplexity
-      # rubocop:disable Metrics/MethodLength
-      # rubocop:disable Metrics/PerceivedComplexity
-
       ##
       # Creates a token object from a key and secret.
       #
@@ -95,12 +90,9 @@ def initialize *args
         raise TypeError, "Expected String, got #{@secret.class}." unless @secret.respond_to? :to_str
         @secret = @secret.to_str
       end
-      # rubocop:enable Metrics/AbcSize
-      # rubocop:enable Metrics/CyclomaticComplexity
-      # rubocop:enable Metrics/MethodLength
-      # rubocop:enable Metrics/PerceivedComplexity
 
-      attr_accessor :key, :secret
+      attr_accessor :key
+      attr_accessor :secret
 
       def to_hash
         {
diff --git a/lib/signet/oauth_1/server.rb b/lib/signet/oauth_1/server.rb
index 0e62a9a..0287640 100644
--- a/lib/signet/oauth_1/server.rb
+++ b/lib/signet/oauth_1/server.rb
@@ -55,15 +55,13 @@ def initialize options = {}
           instance_variable_set "@#{attr}", options[attr]
         end
       end
-      # rubocop:disable Naming/UncommunicativeMethodParamName
 
       # Constant time string comparison.
-      def safe_equals? a, b
-        check = a.bytesize ^ b.bytesize
-        a.bytes.zip(b.bytes) { |x, y| check |= x ^ y.to_i }
+      def safe_equals? left, right
+        check = left.bytesize ^ right.bytesize
+        left.bytes.zip(right.bytes) { |x, y| check |= x ^ y.to_i }
         check.zero?
       end
-      # rubocop:enable Naming/UncommunicativeMethodParamName
 
       ##
       # Determine if the supplied nonce/timestamp pair is valid by calling
@@ -141,8 +139,6 @@ def find_verifier verifier
         verified = @verifier.call verifier if @verifier.respond_to? :call
         verified ? true : false
       end
-      # rubocop:disable Metrics/MethodLength
-      # rubocop:disable Metrics/PerceivedComplexity
 
       ##
       # Validate and normalize the components from an HTTP request.
@@ -188,8 +184,6 @@ def verify_request_components options = {}
         request_components[:body] = body
         request_components
       end
-      # rubocop:enable Metrics/MethodLength
-      # rubocop:enable Metrics/PerceivedComplexity
 
       ##
       # Validate and normalize the HTTP Authorization header.
@@ -199,11 +193,7 @@ def verify_request_components options = {}
       def verify_auth_header_components headers
         auth_header = headers.find { |x| x[0] == "Authorization" }
         raise MalformedAuthorizationError, "Authorization header is missing" if auth_header.nil? || auth_header[1] == ""
-        auth_hash = ::Signet::OAuth1.parse_authorization_header(
-          auth_header[1]
-        ).each_with_object({}) { |(key, val), acc| acc[key.downcase] = val; }
-
-        auth_hash
+        ::Signet::OAuth1.parse_authorization_header(auth_header[1]).to_h.transform_keys(&:downcase)
       end
 
       ##
@@ -232,14 +222,9 @@ def request_realm options = {}
 
         auth_header = request_components[:headers].find { |x| x[0] == "Authorization" }
         raise MalformedAuthorizationError, "Authorization header is missing" if auth_header.nil? || auth_header[1] == ""
-        auth_hash = ::Signet::OAuth1.parse_authorization_header(
-          auth_header[1]
-        ).each_with_object({}) { |(key, val), acc| acc[key.downcase] = val; }
+        auth_hash = ::Signet::OAuth1.parse_authorization_header(auth_header[1]).to_h.transform_keys(&:downcase)
         auth_hash["realm"]
       end
-      # rubocop:disable Metrics/AbcSize
-      # rubocop:disable Metrics/MethodLength
-      # rubocop:disable Metrics/PerceivedComplexity
 
       ##
       # Authenticates a temporary credential request. If no oauth_callback is
@@ -308,7 +293,6 @@ def authenticate_temporary_credential_request options = {}
           false
         end
       end
-      # rubocop:enable Metrics/PerceivedComplexity
 
       ##
       # Authenticates a token credential request.
@@ -379,8 +363,6 @@ def authenticate_token_credential_request options = {}
           temporary_credential: temporary_credential,
           realm:                auth_hash["realm"] }
       end
-      # rubocop:disable Metrics/CyclomaticComplexity
-      # rubocop:disable Metrics/PerceivedComplexity
 
       ##
       # Authenticates a request for a protected resource.
@@ -496,10 +478,6 @@ def authenticate_resource_request options = {}
           token_credential:  token_credential,
           realm:             auth_hash["realm"] }
       end
-      # rubocop:enable Metrics/AbcSize
-      # rubocop:enable Metrics/CyclomaticComplexity
-      # rubocop:enable Metrics/MethodLength
-      # rubocop:enable Metrics/PerceivedComplexity
     end
   end
 end
diff --git a/lib/signet/oauth_1/signature_methods/rsa_sha1.rb b/lib/signet/oauth_1/signature_methods/rsa_sha1.rb
index 5f59958..5a1c3a5 100644
--- a/lib/signet/oauth_1/signature_methods/rsa_sha1.rb
+++ b/lib/signet/oauth_1/signature_methods/rsa_sha1.rb
@@ -11,7 +11,7 @@ def self.generate_signature \
 
 
         private_key = OpenSSL::PKey::RSA.new client_credential_secret
-        signature = private_key.sign OpenSSL::Digest::SHA1.new, base_string
+        signature = private_key.sign OpenSSL::Digest.new("SHA1"), base_string
         # using strict_encode64 because the encode64 method adds newline characters after ever 60 chars
         Base64.strict_encode64(signature).strip
       end
diff --git a/lib/signet/oauth_2.rb b/lib/signet/oauth_2.rb
index 9d8b693..7f805e9 100644
--- a/lib/signet/oauth_2.rb
+++ b/lib/signet/oauth_2.rb
@@ -28,10 +28,10 @@ def self.parse_authorization_header field_value
       case auth_scheme
       when /^Basic$/i
         # HTTP Basic is allowed in OAuth 2
-        return parse_basic_credentials(field_value[/^Basic\s+(.*)$/i, 1])
+        parse_basic_credentials(field_value[/^Basic\s+(.*)$/i, 1])
       when /^OAuth$/i
         # Other token types may be supported eventually
-        return parse_bearer_credentials(field_value[/^OAuth\s+(.*)$/i, 1])
+        parse_bearer_credentials(field_value[/^OAuth\s+(.*)$/i, 1])
       else
         raise ParseError,
               "Parsing non-OAuth Authorization headers is out of scope."
@@ -43,7 +43,7 @@ def self.parse_www_authenticate_header field_value
       case auth_scheme
       when /^OAuth$/i
         # Other token types may be supported eventually
-        return parse_oauth_challenge(field_value[/^OAuth\s+(.*)$/i, 1])
+        parse_oauth_challenge(field_value[/^OAuth\s+(.*)$/i, 1])
       else
         raise ParseError,
               "Parsing non-OAuth WWW-Authenticate headers is out of scope."
@@ -76,9 +76,9 @@ def self.parse_credentials body, content_type
       raise TypeError, "Expected String, got #{body.class}." unless body.is_a? String
       case content_type
       when %r{^application/json.*}
-        return MultiJson.load body
+        MultiJson.load body
       when %r{^application/x-www-form-urlencoded.*}
-        return Hash[Addressable::URI.form_unencode(body)]
+        Hash[Addressable::URI.form_unencode(body)]
       else
         raise ArgumentError, "Invalid content type '#{content_type}'"
       end
@@ -100,9 +100,8 @@ def self.generate_basic_authorization_header client_id, client_password
         raise ArgumentError,
               "A client identifier may not contain a ':' character."
       end
-      "Basic " + Base64.encode64(
-        client_id + ":" + client_password
-      ).delete("\n")
+      token = Base64.encode64("#{client_id}:#{client_password}").delete("\n")
+      "Basic #{token}"
     end
 
     ##
@@ -121,11 +120,8 @@ def self.generate_bearer_authorization_header \
       # TODO: escaping?
       header = "Bearer #{access_token}"
       if auth_params && !auth_params.empty?
-        header += (", " +
-          (auth_params.each_with_object [] do |(key, value), accu|
-            accu << "#{key}=\"#{value}\""
-          end).join(", ")
-                  )
+        additional_headers = auth_params.map { |key, value| "#{key}=\"#{value}\"" }
+        header = ([header] + additional_headers).join ", "
       end
       header
     end
diff --git a/lib/signet/oauth_2/client.rb b/lib/signet/oauth_2/client.rb
index 10cbe00..f6ad0c0 100644
--- a/lib/signet/oauth_2/client.rb
+++ b/lib/signet/oauth_2/client.rb
@@ -110,9 +110,6 @@ def initialize options = {}
         @access_type          = nil
         update! options
       end
-      # rubocop:disable Metrics/AbcSize
-      # rubocop:disable Metrics/CyclomaticComplexity
-      # rubocop:disable Metrics/PerceivedComplexity
 
       ##
       # Updates an OAuth 2.0 client.
@@ -202,13 +199,10 @@ def update! options = {}
         self.signing_key = options[:signing_key] if options.key? :signing_key
         self.extension_parameters = options[:extension_parameters] || {}
         self.additional_parameters = options[:additional_parameters] || {}
-        self.access_type = options.fetch(:access_type) { :offline }
+        self.access_type = options.fetch :access_type, :offline
         update_token! options
         self
       end
-      # rubocop:enable Metrics/AbcSize
-      # rubocop:enable Metrics/CyclomaticComplexity
-      # rubocop:enable Metrics/PerceivedComplexity
 
       ##
       # Updates an OAuth 2.0 client.
@@ -261,10 +255,6 @@ def update_token! options = {}
 
         self
       end
-      # rubocop:disable Metrics/AbcSize
-      # rubocop:disable Metrics/CyclomaticComplexity
-      # rubocop:disable Metrics/MethodLength
-      # rubocop:disable Metrics/PerceivedComplexity
 
       ##
       # Returns the authorization URI that the user should be redirected to.
@@ -290,9 +280,7 @@ def authorization_uri options = {}
         options[:state] = state unless options[:state]
         options.merge!(additional_parameters.merge(options[:additional_parameters] || {}))
         options.delete :additional_parameters
-        options = Hash[options.map do |key, option|
-          [key.to_s, option]
-        end]
+        options = options.transform_keys(&:to_s)
         uri = Addressable::URI.parse(
           ::Signet::OAuth2.generate_authorization_uri(
             @authorization_uri, options
@@ -304,10 +292,6 @@ def authorization_uri options = {}
         end
         uri
       end
-      # rubocop:enable Metrics/AbcSize
-      # rubocop:enable Metrics/CyclomaticComplexity
-      # rubocop:enable Metrics/MethodLength
-      # rubocop:enable Metrics/PerceivedComplexity
 
       ##
       # Sets the authorization URI for this client.
@@ -423,7 +407,7 @@ def scope= new_scope
           end
           @scope = new_scope
         when String
-          @scope = new_scope.split " "
+          @scope = new_scope.split
         when nil
           @scope = nil
         else
@@ -793,12 +777,12 @@ def expires_in
       # @param [String, Integer, nil] new_expires_in
       #   The access token lifetime.
       def expires_in= new_expires_in
-        if !new_expires_in.nil?
-          @issued_at = Time.now
-          @expires_at = @issued_at + new_expires_in.to_i
-        else
+        if new_expires_in.nil?
           @expires_at = nil
           @issued_at = nil
+        else
+          @issued_at = Time.now
+          @expires_at = @issued_at + new_expires_in.to_i
         end
       end
 
@@ -922,8 +906,6 @@ def to_jwt options = {}
         assertion["sub"] = sub unless sub.nil?
         JWT.encode assertion, signing_key, signing_algorithm
       end
-      # rubocop:disable Style/MethodDefParentheses
-      # rubocop:disable Metrics/AbcSize
 
       ##
       # Serialize the client object to JSON.
@@ -931,7 +913,7 @@ def to_jwt options = {}
       # @note A serialized client contains sensitive information. Persist or transmit with care.
       #
       # @return [String] A serialized JSON representation of the client.
-      def to_json(*)
+      def to_json *_args
         MultiJson.dump(
           "authorization_uri"    => authorization_uri ? authorization_uri.to_s : nil,
           "token_credential_uri" => token_credential_uri ? token_credential_uri.to_s : nil,
@@ -956,10 +938,6 @@ def to_json(*)
           "extension_parameters" => extension_parameters
         )
       end
-      # rubocop:enable Style/MethodDefParentheses
-      # rubocop:disable Metrics/CyclomaticComplexity
-      # rubocop:disable Metrics/MethodLength
-      # rubocop:disable Metrics/PerceivedComplexity
 
       ##
       # Generates a request for token credentials.
@@ -1005,8 +983,6 @@ def generate_access_token_request options = {}
         additional.each { |k, v| parameters[k.to_s] = v }
         parameters
       end
-      # rubocop:enable Metrics/CyclomaticComplexity
-      # rubocop:enable Metrics/PerceivedComplexity
 
       def fetch_access_token options = {}
         raise ArgumentError, "Missing token endpoint URI." if token_credential_uri.nil?
@@ -1035,20 +1011,16 @@ def fetch_access_token options = {}
 
         message = "  Server message:\n#{response.body.to_s.strip}" unless body.to_s.strip.empty?
         if [400, 401, 403].include? status
-          message = "Authorization failed." + message
-          raise ::Signet::AuthorizationError.new(
-            message, response: response
-          )
+          message = "Authorization failed.#{message}"
+          raise ::Signet::AuthorizationError.new message, response: response
         elsif status.to_s[0] == "5"
-          message = "Remote server error." + message
+          message = "Remote server error.#{message}"
           raise ::Signet::RemoteServerError, message
         else
-          message = "Unexpected status code: #{response.status}." + message
+          message = "Unexpected status code: #{response.status}.#{message}"
           raise ::Signet::UnexpectedStatusError, message
         end
       end
-      # rubocop:enable Metrics/AbcSize
-      # rubocop:enable Metrics/MethodLength
 
       def fetch_access_token! options = {}
         token_hash = fetch_access_token options
@@ -1068,9 +1040,6 @@ def fetch_access_token! options = {}
       def refresh! options = {}
         fetch_access_token! options
       end
-      # rubocop:disable Metrics/AbcSize
-      # rubocop:disable Metrics/MethodLength
-      # rubocop:disable Metrics/PerceivedComplexity
 
       ##
       # Generates an authenticated request for protected resources.
@@ -1137,9 +1106,6 @@ def generate_authenticated_request options = {}
         request["Cache-Control"] = "no-store"
         request
       end
-      # rubocop:enable Metrics/AbcSize
-      # rubocop:enable Metrics/MethodLength
-      # rubocop:enable Metrics/PerceivedComplexity
 
       ##
       # Transmits a request for a protected resource.
diff --git a/rakelib/devsite_builder.rb b/rakelib/devsite_builder.rb
index 06ebb7a..3b25cd6 100644
--- a/rakelib/devsite_builder.rb
+++ b/rakelib/devsite_builder.rb
@@ -1,6 +1,6 @@
 require "pathname"
 
-require_relative "repo_metadata.rb"
+require_relative "repo_metadata"
 
 class DevsiteBuilder
   def initialize master_dir = "."
diff --git a/rakelib/repo_metadata.rb b/rakelib/repo_metadata.rb
index f371230..3fb8cc1 100644
--- a/rakelib/repo_metadata.rb
+++ b/rakelib/repo_metadata.rb
@@ -23,7 +23,7 @@ def build output_directory
   end
 
   def normalize_data!
-    require_relative "../lib/signet/version.rb"
+    require_relative "../lib/signet/version"
 
     @data.delete_if { |k, _| !allowed_fields.include?(k) }
     @data["version"] = "v#{Signet::VERSION}"
diff --git a/signet.gemspec b/signet.gemspec
index 4e22c90..2f5ed35 100644
--- a/signet.gemspec
+++ b/signet.gemspec
@@ -21,14 +21,15 @@ Gem::Specification.new do |gem|
   gem.homepage = "https://github.com/googleapis/signet"
   gem.rdoc_options = ["--main", "README.md"]
   gem.summary = "Signet is an OAuth 1.0 / OAuth 2.0 implementation."
-  gem.required_ruby_version = ">= 2.4.0"
+
+  gem.required_ruby_version = ">= 2.5"
 
   gem.add_runtime_dependency "addressable", "~> 2.3"
   gem.add_runtime_dependency "faraday", ">= 0.17.3", "< 2.0"
   gem.add_runtime_dependency "jwt", ">= 1.5", "< 3.0"
   gem.add_runtime_dependency "multi_json", "~> 1.10"
 
-  gem.add_development_dependency "google-style", "~> 0.3"
+  gem.add_development_dependency "google-style", "~> 1.25.1"
   gem.add_development_dependency "kramdown", "~> 1.5"
   gem.add_development_dependency "launchy", "~> 2.4"
   gem.add_development_dependency "rake", "~> 12.0"