diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index b58214ae..90977e9a 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -13,14 +13,11 @@ jobs:
     name: Tests
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v4
     - uses: ruby/setup-ruby@v1
       with:
-        ruby-version: 3.1
-    - name: Install dependencies
-      run: |
-        gem install bundler
-        bundle install
+        ruby-version: 3.3
+        bundler-cache: true
     - name: Run tests
       run: |
         bundle exec ruby test_data.rb
diff --git a/.ruby-version b/.ruby-version
index ef538c28..fa7adc7a 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-3.1.2
+3.3.5
diff --git a/Gemfile b/Gemfile
index 21aa6317..4243849d 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,7 +1,8 @@
 source "https://rubygems.org"
 
+gem "csv"
 gem "luhnacy"
-gem "stringex", "~> 2.5.2"
-gem "minitest", "~> 5.6.0"
+gem "stringex", "~> 2.8"
+gem "minitest", "~> 5.25"
 gem "minitest-focus"
-gem "tzinfo", "~> 1.2.10"
+gem "tzinfo", "~> 2.0"
diff --git a/Gemfile.lock b/Gemfile.lock
index 3e49814b..a9e697b9 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,24 +1,35 @@
 GEM
   remote: https://rubygems.org/
   specs:
+    concurrent-ruby (1.3.4)
+    csv (3.3.0)
     luhnacy (0.2.2)
-    minitest (5.6.1)
-    minitest-focus (1.1.2)
+    minitest (5.25.1)
+    minitest-focus (1.4.0)
       minitest (>= 4, < 6)
-    stringex (2.5.2)
-    thread_safe (0.3.6)
-    tzinfo (1.2.10)
-      thread_safe (~> 0.1)
+    stringex (2.8.6)
+    tzinfo (2.0.6)
+      concurrent-ruby (~> 1.0)
 
 PLATFORMS
   ruby
 
 DEPENDENCIES
+  csv
   luhnacy
-  minitest (~> 5.6.0)
+  minitest (~> 5.25)
   minitest-focus
-  stringex (~> 2.5.2)
-  tzinfo (~> 1.2.10)
+  stringex (~> 2.8)
+  tzinfo (~> 2.0)
+
+CHECKSUMS
+  concurrent-ruby (1.3.4) sha256=d4aa926339b0a86b5b5054a0a8c580163e6f5dcbdfd0f4bb916b1a2570731c32
+  csv (3.3.0) sha256=0bbd1defdc31134abefed027a639b3723c2753862150f4c3ee61cab71b20d67d
+  luhnacy (0.2.2) sha256=81d12741f96128c751790531ecec667422ac6bd80e6dd18b6330692f34359080
+  minitest (5.25.1) sha256=3db6795a80634def1cf86fda79d2d83b59b25ce5e186fa675f73c565589d2ad8
+  minitest-focus (1.4.0) sha256=4cf04bd2b5fe0649922db56f9f2ae30af91475a0f51e02c2baa33f5c5a47ff6c
+  stringex (2.8.6) sha256=c7b382d2b2a47a1e1646f256df201c48d487d6296fbb289d76802f67f5e929c4
+  tzinfo (2.0.6) sha256=8daf828cc77bcf7d63b0e3bdb6caa47e2272dcfaf4fbfe46f8c3a9df087a829b
 
 BUNDLED WITH
-   1.17.2
+   2.5.16
diff --git a/test_data.rb b/test_data.rb
index b96fb7d9..a5a4bbaf 100644
--- a/test_data.rb
+++ b/test_data.rb
@@ -83,7 +83,7 @@ def test_is_station_useful
 
   def test_valid_timezone
     Constants::COUNTRIES.values.each do |timezone|
-      tz = TZInfo::Timezone.get(timezone)
+      assert TZInfo::Timezone.get(timezone)
     end
   end