diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..846eab1
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,24 @@
+name: CI
+on:
+  pull_request:
+    branches:
+      - '**'
+  push:
+    branches:
+      - master
+jobs:
+  build:
+    name: Ruby ${{ matrix.version }}
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        version: [ '2.7', '3.0', '3.1', '3.2', '3.3' ]
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up Ruby ${{ matrix.version }}
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.version }}
+          bundler-cache: true
+      - name: Test
+        run: bundle exec rake test
diff --git a/.gitignore b/.gitignore
index 2ac8271..247384c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,4 +2,3 @@ pkg/*
 *.gem
 .bundle
 .DS_Store
-Gemfile.lock
diff --git a/.ruby-version b/.ruby-version
new file mode 100644
index 0000000..a603bb5
--- /dev/null
+++ b/.ruby-version
@@ -0,0 +1 @@
+2.7.5
diff --git a/Gemfile.lock b/Gemfile.lock
new file mode 100644
index 0000000..af108c7
--- /dev/null
+++ b/Gemfile.lock
@@ -0,0 +1,49 @@
+PATH
+  remote: .
+  specs:
+    active_utils (3.4.1)
+      activesupport (>= 4.2)
+      i18n
+
+GEM
+  remote: https://rubygems.org/
+  specs:
+    activesupport (7.1.3.2)
+      base64
+      bigdecimal
+      concurrent-ruby (~> 1.0, >= 1.0.2)
+      connection_pool (>= 2.2.5)
+      drb
+      i18n (>= 1.6, < 2)
+      minitest (>= 5.1)
+      mutex_m
+      tzinfo (~> 2.0)
+    base64 (0.2.0)
+    bigdecimal (3.1.7)
+    concurrent-ruby (1.2.3)
+    connection_pool (2.4.1)
+    drb (2.2.1)
+    i18n (1.14.4)
+      concurrent-ruby (~> 1.0)
+    minitest (5.22.3)
+    mocha (2.1.0)
+      ruby2_keywords (>= 0.0.5)
+    mutex_m (0.2.0)
+    rake (13.2.0)
+    ruby2_keywords (0.0.5)
+    tzinfo (2.0.6)
+      concurrent-ruby (~> 1.0)
+
+PLATFORMS
+  arm64-darwin-21
+  arm64-darwin-23
+  x86_64-linux
+
+DEPENDENCIES
+  active_utils!
+  minitest
+  mocha
+  rake
+
+BUNDLED WITH
+   2.4.18
diff --git a/Rakefile b/Rakefile
index 970da8e..93c066c 100644
--- a/Rakefile
+++ b/Rakefile
@@ -5,7 +5,6 @@ require 'rake/testtask'
 
 Rake::TestTask.new(:test) do |t|
   t.pattern = 'test/unit/**/*_test.rb'
-  t.ruby_opts << '-rubygems'
   t.libs << 'test'
   t.verbose = true
 end
diff --git a/active_utils.gemspec b/active_utils.gemspec
index 185d0c0..e3b59c0 100644
--- a/active_utils.gemspec
+++ b/active_utils.gemspec
@@ -12,6 +12,8 @@ Gem::Specification.new do |s|
   s.summary     = %q{Common utils used by active_merchant, active_fulfillment, and active_shipping}
   s.license     = 'MIT'
 
+  s.required_ruby_version = ">= 2.7"
+
   s.rubyforge_project = "active_utils"
 
   s.add_dependency('activesupport', '>= 4.2')
diff --git a/lib/active_utils/country.rb b/lib/active_utils/country.rb
index c905f13..a36b04e 100644
--- a/lib/active_utils/country.rb
+++ b/lib/active_utils/country.rb
@@ -66,7 +66,6 @@ def to_s
       { :alpha2 => 'AF', :name => 'Afghanistan', :alpha3 => 'AFG', :numeric => '004' },
       { :alpha2 => 'AX', :name => 'Aland Islands', :alpha3 => 'ALA', :numeric => '248' },
       { :alpha2 => 'AL', :name => 'Albania', :alpha3 => 'ALB', :numeric => '008' },
-      { :alpha2 => 'AC', :name => 'Ascension Island', :alpha3 => 'ASC' },
       { :alpha2 => 'DZ', :name => 'Algeria', :alpha3 => 'DZA', :numeric => '012' },
       { :alpha2 => 'AS', :name => 'American Samoa', :alpha3 => 'ASM', :numeric => '016' },
       { :alpha2 => 'AD', :name => 'Andorra', :alpha3 => 'AND', :numeric => '020' },
@@ -77,6 +76,7 @@ def to_s
       { :alpha2 => 'AR', :name => 'Argentina', :alpha3 => 'ARG', :numeric => '032' },
       { :alpha2 => 'AM', :name => 'Armenia', :alpha3 => 'ARM', :numeric => '051' },
       { :alpha2 => 'AW', :name => 'Aruba', :alpha3 => 'ABW', :numeric => '533' },
+      { :alpha2 => 'AC', :name => 'Ascension Island', :alpha3 => 'ASC' },
       { :alpha2 => 'AU', :name => 'Australia', :alpha3 => 'AUS', :numeric => '036' },
       { :alpha2 => 'AT', :name => 'Austria', :alpha3 => 'AUT', :numeric => '040' },
       { :alpha2 => 'AZ', :name => 'Azerbaijan', :alpha3 => 'AZE', :numeric => '031' },
diff --git a/test/unit/connection_test.rb b/test/unit/connection_test.rb
index 655497b..6b971d3 100644
--- a/test/unit/connection_test.rb
+++ b/test/unit/connection_test.rb
@@ -11,7 +11,7 @@ def setup
   end
 
   def test_path_to_cert_is_correct
-    assert File.exists?(ActiveUtils::Connection::CA_FILE)
+    assert File.file?(ActiveUtils::Connection::CA_FILE)
   end
 
   def test_connection_endpoint_parses_string_to_uri
@@ -130,8 +130,8 @@ def test_override_ca_path
     assert_equal "/bogus", @connection.send(:http).ca_path
   end
 
-  def test_default_proxy_address_is_nil
-    assert_equal nil, @connection.proxy_address
+  def test_default_proxy_address_is_env
+    assert_equal :ENV, @connection.proxy_address
   end
 
   def test_default_proxy_port_is_nil
diff --git a/test/unit/posts_data_test.rb b/test/unit/posts_data_test.rb
index 4cade9a..ca19d64 100644
--- a/test/unit/posts_data_test.rb
+++ b/test/unit/posts_data_test.rb
@@ -2,7 +2,6 @@
 require 'active_support/core_ext/class'
 
 class PostsDataTest < Minitest::Test
-
   class SSLPoster
     include PostsData
 
@@ -44,6 +43,8 @@ def test_logger_warns_if_ssl_strict_disabled
 
     SSLPoster.ssl_strict = false
     @poster.raw_ssl_request(:post, "https://shopify.com", "", {})
+  ensure
+    SSLPoster.ssl_strict = true
   end
 
   def test_logger_warns_can_handle_non_string_endpoints
@@ -65,10 +66,15 @@ def test_logger_no_warning_if_ssl_strict_enabled
   end
 
   def test_set_proxy_address_and_port
+    original_proxy_address = SSLPoster.proxy_address
+    original_proxy_port = SSLPoster.proxy_port
     SSLPoster.proxy_address = 'http://proxy.example.com'
     SSLPoster.proxy_port = '8888'
     assert_equal @poster.proxy_address, 'http://proxy.example.com'
     assert_equal @poster.proxy_port, '8888'
+  ensure
+    SSLPoster.proxy_address = original_proxy_address
+    SSLPoster.proxy_port = original_proxy_port
   end
 
   class HttpConnectionAbort < StandardError; end