diff --git a/.rubocop.yml b/.rubocop.yml
index 909d0f3..c75c9ca 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,8 +1,11 @@
 AllCops:
   NewCops: disable
   SuggestExtensions: false
+  Exclude:
+    - bin/*
 
 plugins:
+  - rubocop-performance
   - rubocop-rspec
   - rubocop-rake
 
@@ -65,4 +68,4 @@ RSpec/SpecFilePathFormat:
 RSpec/ContextWording:
   Enabled: false
 RSpec/OverwritingSetup:
-  Enabled: false
\ No newline at end of file
+  Enabled: false
diff --git a/Gemfile b/Gemfile
index 33b0fb1..42764f4 100644
--- a/Gemfile
+++ b/Gemfile
@@ -7,3 +7,15 @@ gemspec
 
 gem 'json', '~> 2.1'
 gem 'mini_mime'
+gem 'pry', '~> 0.16.0'
+gem 'rails'
+gem 'rake', '~> 13.3.1'
+gem 'rspec', '~> 3.13.0'
+gem 'rspec-its', '~> 2.0.0'
+gem 'rubocop'
+gem 'rubocop-performance'
+gem 'rubocop-rake'
+gem 'rubocop-rspec'
+gem 'simplecov'
+gem 'vcr', '~> 6.4.0'
+gem 'webmock', '~> 3.7'
diff --git a/Rakefile b/Rakefile
index 64831bc..be9a038 100644
--- a/Rakefile
+++ b/Rakefile
@@ -29,4 +29,4 @@ RSpec::Core::RakeTask.new('spec:all') do |t|
   t.pattern = 'spec/**/*_spec.rb'
 end
 
-task default: 'spec:unit'
+task default: 'spec:all'
diff --git a/bin/rake b/bin/rake
new file mode 100755
index 0000000..9efbee9
--- /dev/null
+++ b/bin/rake
@@ -0,0 +1,16 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+#
+# This file was generated by Bundler.
+#
+# The application 'rake' is installed as part of a gem, and
+# this file is here to facilitate running it.
+#
+
+ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../Gemfile", __dir__)
+
+require "rubygems"
+require "bundler/setup"
+
+load Gem.bin_path("rake", "rake")
diff --git a/bin/rspec b/bin/rspec
new file mode 100755
index 0000000..93e191c
--- /dev/null
+++ b/bin/rspec
@@ -0,0 +1,16 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+#
+# This file was generated by Bundler.
+#
+# The application 'rspec' is installed as part of a gem, and
+# this file is here to facilitate running it.
+#
+
+ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../Gemfile", __dir__)
+
+require "rubygems"
+require "bundler/setup"
+
+load Gem.bin_path("rspec-core", "rspec")
diff --git a/bin/rubocop b/bin/rubocop
new file mode 100755
index 0000000..d73598d
--- /dev/null
+++ b/bin/rubocop
@@ -0,0 +1,16 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+#
+# This file was generated by Bundler.
+#
+# The application 'rubocop' is installed as part of a gem, and
+# this file is here to facilitate running it.
+#
+
+ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../Gemfile", __dir__)
+
+require "rubygems"
+require "bundler/setup"
+
+load Gem.bin_path("rubocop", "rubocop")
diff --git a/lib/mailgun/client.rb b/lib/mailgun/client.rb
index 0e84e78..5ff36f7 100644
--- a/lib/mailgun/client.rb
+++ b/lib/mailgun/client.rb
@@ -27,7 +27,7 @@ def initialize(api_key = Mailgun.api_key,
           'Accept' => '*/*'
         }
       }
-      request_options.merge!(request: { timeout: timeout }) if timeout
+      request_options[:request] = { timeout: timeout } if timeout
 
       @http_client = build_http_client(api_key, request_options)
 
diff --git a/lib/mailgun/helpers/api_version_checker.rb b/lib/mailgun/helpers/api_version_checker.rb
index 463bf3d..daf454a 100644
--- a/lib/mailgun/helpers/api_version_checker.rb
+++ b/lib/mailgun/helpers/api_version_checker.rb
@@ -13,7 +13,7 @@ def requires_api_version(version, *method_names)
 
           define_method(method_name) do |*args, **kwargs, &block|
             warn_unless_api_version(version)
-            original_method.bind(self).call(*args, **kwargs, &block)
+            original_method.bind_call(self, *args, **kwargs, &block)
           end
         end
       end
@@ -24,7 +24,7 @@ def enforces_api_version(version, *method_names)
 
           define_method(method_name) do |*args, **kwargs, &block|
             require_api_version(version)
-            original_method.bind(self).call(*args, **kwargs, &block)
+            original_method.bind_call(self, *args, **kwargs, &block)
           end
         end
       end
diff --git a/lib/mailgun/response.rb b/lib/mailgun/response.rb
index bc0d2fd..646f299 100644
--- a/lib/mailgun/response.rb
+++ b/lib/mailgun/response.rb
@@ -65,7 +65,7 @@ def to_yaml!
     #
     # @return [Boolean] A boolean that binarizes the response status result.
     def success?
-      (200..299).include?(status)
+      (200..299).cover?(status)
     end
   end
 end
diff --git a/mailgun.gemspec b/mailgun.gemspec
index 5fbd3ee..c6b08b4 100644
--- a/mailgun.gemspec
+++ b/mailgun.gemspec
@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-lib = File.expand_path('lib', __dir__)
-$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
-require 'mailgun/version'
+require_relative 'lib/mailgun/version'
 
 Gem::Specification.new do |spec|
   spec.name             = 'mailgun-ruby'
@@ -20,26 +18,10 @@ Gem::Specification.new do |spec|
   spec.metadata['documentation_uri'] = 'https://documentation.mailgun.com/'
   spec.metadata['source_code_uri'] = 'https://github.com/mailgun/mailgun-ruby'
 
-  spec.files         = `git ls-files -z`.split("\x0")
-  spec.executables   = spec.files.grep(%r{^bin/}) { |f| File.basename(f) }
-  spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
-  spec.require_paths = ['lib']
+  spec.files = Dir['README.md', 'LICENSE', 'CHANGELOG.md', 'lib/**/*.rb']
 
   spec.required_ruby_version = '>= 3.0.0'
 
-  spec.add_development_dependency 'bundler', '>= 1.16.2'
-  spec.add_development_dependency 'pry', '~> 0.16.0'
-  spec.add_development_dependency 'rails'
-  spec.add_development_dependency 'rake', '~> 13.3.1'
-  spec.add_development_dependency 'rspec', '~> 3.13.0'
-  spec.add_development_dependency 'rspec-its', '~> 2.0.0'
-  spec.add_development_dependency 'rubocop'
-  spec.add_development_dependency 'rubocop-rake'
-  spec.add_development_dependency 'rubocop-rspec'
-  spec.add_development_dependency 'simplecov'
-  spec.add_development_dependency 'simplecov-json'
-  spec.add_development_dependency 'vcr', '~> 6.4.0'
-  spec.add_development_dependency 'webmock', '~> 3.7'
   spec.add_dependency 'faraday', '~> 2.1'
   spec.add_dependency 'faraday-multipart', '< 2'
   spec.add_dependency 'mini_mime'
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 16dd7ef..fdd97a1 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -1,7 +1,8 @@
 # frozen_string_literal: true
 
 require 'simplecov'
-require 'simplecov-json'
+require 'simplecov_json_formatter'
+
 SimpleCov.formatters = SimpleCov::Formatter::MultiFormatter.new(
   [
     SimpleCov::Formatter::HTMLFormatter,