diff --git a/.devcontainer/devcontainer.json b/.devcontainer/devcontainer.json
index 911646f..ecea0e3 100644
--- a/.devcontainer/devcontainer.json
+++ b/.devcontainer/devcontainer.json
@@ -6,6 +6,9 @@
 
 	"features": {
 		"ghcr.io/devcontainers/features/docker-in-docker:2": {},
+		"ghcr.io/rails/devcontainer/features/ruby": {
+			"version": "4.0.1"
+		},
 		"ghcr.io/devcontainers/features/github-cli": {}
 	},
 
diff --git a/.github/ruby-versions.json b/.github/ruby-versions.json
new file mode 100644
index 0000000..f9a4c32
--- /dev/null
+++ b/.github/ruby-versions.json
@@ -0,0 +1,33 @@
+[
+    "4.0.0",
+    "3.4.8",
+    "3.4.7",
+    "3.4.6",
+    "3.4.5",
+    "3.4.4",
+    "3.4.3",
+    "3.4.2",
+    "3.4.1",
+    "3.4.0",
+    "3.3.10",
+    "3.3.9",
+    "3.3.8",
+    "3.3.7",
+    "3.3.6",
+    "3.3.5",
+    "3.3.4",
+    "3.3.3",
+    "3.3.2",
+    "3.3.1",
+    "3.3.0",
+    "3.2.9",
+    "3.2.8",
+    "3.2.7",
+    "3.2.6",
+    "3.2.5",
+    "3.2.4",
+    "3.2.3",
+    "3.2.2",
+    "3.2.1",
+    "3.2.0"
+]
diff --git a/.github/workflows/publish-new-image-version.yaml b/.github/workflows/publish-new-image-version.yaml
index 40858de..55de5af 100644
--- a/.github/workflows/publish-new-image-version.yaml
+++ b/.github/workflows/publish-new-image-version.yaml
@@ -4,43 +4,22 @@ name: Build and Publish Images
     tags:
       - ruby-*.*.*
 jobs:
+  setup:
+    runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.set-matrix.outputs.matrix }}
+    steps:
+      - uses: actions/checkout@v4
+      - id: set-matrix
+        run: echo "matrix=$(cat .github/ruby-versions.json | jq -c '.')" >> $GITHUB_OUTPUT
+
   build:
     name: Build Images
+    needs: setup
     strategy:
       fail-fast: false
       matrix:
-        RUBY_VERSION:
-          - 4.0.0
-          - 3.4.8
-          - 3.4.7
-          - 3.4.6
-          - 3.4.5
-          - 3.4.4
-          - 3.4.3
-          - 3.4.2
-          - 3.4.1
-          - 3.4.0
-          - 3.3.10
-          - 3.3.9
-          - 3.3.8
-          - 3.3.7
-          - 3.3.6
-          - 3.3.5
-          - 3.3.4
-          - 3.3.3
-          - 3.3.2
-          - 3.3.1
-          - 3.3.0
-          - 3.2.9
-          - 3.2.8
-          - 3.2.7
-          - 3.2.6
-          - 3.2.5
-          - 3.2.4
-          - 3.2.3
-          - 3.2.2
-          - 3.2.1
-          - 3.2.0
+        RUBY_VERSION: ${{ fromJSON(needs.setup.outputs.matrix) }}
     runs-on: ubuntu-latest
     permissions:
       contents: read
diff --git a/.github/workflows/test-features.yaml b/.github/workflows/test-features.yaml
index 7734283..d63025f 100644
--- a/.github/workflows/test-features.yaml
+++ b/.github/workflows/test-features.yaml
@@ -65,3 +65,33 @@ jobs:
       - name: "Run shellcheck"
         working-directory: features
         run: find . -name "*.sh" -type f -exec shellcheck {} +
+
+  ruby-tests:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: .ruby-version
+          bundler-cache: true
+
+      - name: Run tests
+        run: bundle exec rake test
+
+  ci:
+    runs-on: ubuntu-latest
+    needs: [test-autogenerated, test-scenarios, shellcheck, ruby-tests]
+    if: always()
+    steps:
+      - name: Check CI status
+        run: |
+          if [[ "${{ needs.test-autogenerated.result }}" == "failure" ]] || \
+             [[ "${{ needs.test-scenarios.result }}" == "failure" ]] || \
+             [[ "${{ needs.shellcheck.result }}" == "failure" ]] || \
+             [[ "${{ needs.ruby-tests.result }}" == "failure" ]]; then
+            echo "One or more jobs failed"
+            exit 1
+          fi
+          echo "All jobs passed successfully"
diff --git a/.ruby-version b/.ruby-version
new file mode 100644
index 0000000..1454f6e
--- /dev/null
+++ b/.ruby-version
@@ -0,0 +1 @@
+4.0.1
diff --git a/Gemfile b/Gemfile
new file mode 100644
index 0000000..0231c8a
--- /dev/null
+++ b/Gemfile
@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+source "https://rubygems.org"
+
+gem "minitest"
+gem "rake"
diff --git a/Gemfile.lock b/Gemfile.lock
new file mode 100644
index 0000000..6a44429
--- /dev/null
+++ b/Gemfile.lock
@@ -0,0 +1,23 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    minitest (6.0.1)
+      prism (~> 1.5)
+    prism (1.9.0)
+    rake (13.3.1)
+
+PLATFORMS
+  aarch64-linux
+  ruby
+
+DEPENDENCIES
+  minitest
+  rake
+
+CHECKSUMS
+  minitest (6.0.1) sha256=7854c74f48e2e975969062833adc4013f249a4b212f5e7b9d5c040bf838d54bb
+  prism (1.9.0) sha256=7b530c6a9f92c24300014919c9dcbc055bf4cdf51ec30aed099b06cd6674ef85
+  rake (13.3.1) sha256=8c9e89d09f66a26a01264e7e3480ec0607f0c497a861ef16063604b1b08eb19c
+
+BUNDLED WITH
+  4.0.3
diff --git a/Rakefile b/Rakefile
new file mode 100644
index 0000000..995b134
--- /dev/null
+++ b/Rakefile
@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+require "rake/testtask"
+
+Rake::TestTask.new(:test) do |t|
+  t.libs << "test"
+  t.pattern = "test/**/*_test.rb"
+  t.verbose = true
+end
+
+task default: :test
diff --git a/bin/add-ruby-version b/bin/add-ruby-version
index 550991d..f6319f1 100755
--- a/bin/add-ruby-version
+++ b/bin/add-ruby-version
@@ -1,443 +1,13 @@
-#!/usr/bin/env node
+#!/usr/bin/env ruby
+# frozen_string_literal: true
 
-/**
- * Ruby Version Management Script
- *
- * This script automates the process of adding new Ruby versions to the devcontainer
- * configuration. It updates the GitHub workflow matrix, potentially updates the
- * default Ruby version, bumps the feature version, and updates test files.
- *
- * Usage: bin/add-ruby-version <ruby-version>
- * Example: bin/add-ruby-version 3.4.5
- *
- * The script will:
- * 1. Validate the version format
- * 2. Check if the version already exists
- * 3. Add the version to the workflow matrix
- * 4. Update the default version if the new version is newer
- * 5. Update the README.md default version
- * 6. Bump the feature version when the default changes
- * 7. Update test files to use the new version
- *
- * @author Rails Team
- * @version 1.0.0
- */
+require_relative "../lib/add_ruby_version"
 
-const fs = require('fs');
-const yaml = require('js-yaml');
-const semver = require('semver');
+if ARGV.length != 1
+  warn "Usage: bin/add-ruby-version <ruby-version>"
+  warn "Example: bin/add-ruby-version 3.4.5"
+  exit 1
+end
 
-// ANSI color codes for better output
-const colors = {
-    reset: '\x1b[0m',
-    green: '\x1b[32m',
-    blue: '\x1b[34m',
-    yellow: '\x1b[33m',
-    red: '\x1b[31m',
-    cyan: '\x1b[36m',
-    magenta: '\x1b[35m'
-};
-
-// Regex patterns for version handling
-const VERSION_PATTERN = '\\d+\\.\\d+\\.\\d+';
-const VERSION_VALIDATION_REGEX = new RegExp(`^${VERSION_PATTERN}$`);
-const VERSION_REPLACEMENT_REGEX = new RegExp(`(${VERSION_PATTERN})`, 'g');
-
-// File paths
-const YAML_FILE = '.github/workflows/publish-new-image-version.yaml';
-const JSON_FILE = 'features/src/ruby/devcontainer-feature.json';
-const README_FILE = 'features/src/ruby/README.md';
-const TEST_FILES = [
-    'features/test/ruby/test.sh',
-    'features/test/ruby/with_rbenv.sh'
-];
-
-// YAML formatting options
-const YAML_DUMP_OPTIONS = {
-    indent: 2,
-    lineWidth: -1,
-    noRefs: true,
-    sortKeys: false,
-    noArrayIndent: false,
-    skipInvalid: false,
-    flowLevel: -1,
-    styles: {},
-    schema: yaml.DEFAULT_SCHEMA,
-    noCompatMode: false,
-    condenseFlow: false,
-    quotingType: '"',
-    forceQuotes: false
-};
-
-// Emoji helpers
-const emoji = {
-    search: '🔍',
-    edit: '📝',
-    check: '✅',
-    update: '🔄',
-    info: 'ℹ️',
-    party: '🎉',
-    file: '📄',
-    bulb: '💡',
-    error: '❌'
-};
-
-/**
- * Logs a message with optional color formatting
- * @param {string} message - The message to log
- * @param {string} color - The color to use (default: 'reset')
- */
-function log(message, color = 'reset') {
-    console.log(colors[color] + message + colors.reset);
-}
-
-/**
- * Logs an error message and exits the process
- * @param {string} message - The error message to display
- */
-function exitWithError(message) {
-    log(`${emoji.error} Error: ${message}`, 'red');
-    process.exit(1);
-}
-
-// === FILE OPERATIONS ===
-/**
- * Checks if a file exists, exits with error if not found
- * @param {string} filePath - The path to check
- */
-function checkFileExists(filePath) {
-    if (!fs.existsSync(filePath)) {
-        log(`${emoji.error} Error: ${filePath} not found`, 'red');
-        process.exit(1);
-    }
-}
-
-/**
- * Reads and parses a JSON file
- * @param {string} filePath - The path to the JSON file
- * @returns {Object} The parsed JSON data
- */
-function readJsonFile(filePath) {
-    try {
-        const content = fs.readFileSync(filePath, 'utf8');
-        return JSON.parse(content);
-    } catch (error) {
-        throw new Error(`Could not read JSON file ${filePath}: ${error.message}`);
-    }
-}
-
-/**
- * Writes data to a JSON file with formatting
- * @param {string} filePath - The path to write to
- * @param {Object} data - The data to write
- */
-function writeJsonFile(filePath, data) {
-    try {
-        fs.writeFileSync(filePath, JSON.stringify(data, null, 4) + '\n');
-    } catch (error) {
-        throw new Error(`Could not write JSON file ${filePath}: ${error.message}`);
-    }
-}
-
-/**
- * Reads and parses a YAML file
- * @param {string} filePath - The path to the YAML file
- * @returns {Object} The parsed YAML data
- */
-function readYamlFile(filePath) {
-    try {
-        const content = fs.readFileSync(filePath, 'utf8');
-        return yaml.load(content);
-    } catch (error) {
-        throw new Error(`Could not read YAML file ${filePath}: ${error.message}`);
-    }
-}
-
-/**
- * Writes data to a YAML file with formatting
- * @param {string} filePath - The path to write to
- * @param {Object} data - The data to write
- */
-function writeYamlFile(filePath, data) {
-    try {
-        const content = yaml.dump(data, YAML_DUMP_OPTIONS);
-        fs.writeFileSync(filePath, content);
-    } catch (error) {
-        throw new Error(`Could not write YAML file ${filePath}: ${error.message}`);
-    }
-}
-
-/**
- * Updates version numbers in test files using regex replacement
- * @param {string} newVersion - The new version to replace with
- * @param {string} testFile - The test file to update
- * @returns {boolean} Success status
- */
-function updateVersionInTestFile(newVersion, testFile) {
-    try {
-        const content = fs.readFileSync(testFile, 'utf8');
-        const updatedContent = content.replace(VERSION_REPLACEMENT_REGEX, newVersion);
-        fs.writeFileSync(testFile, updatedContent);
-        return true;
-    } catch (error) {
-        throw new Error(`Could not update test file ${testFile}: ${error.message}`);
-    }
-}
-
-/**
- * Updates the default version in the README.md file
- * @param {string} newVersion - The new default version
- * @param {string} readmeFile - Path to the README.md file
- * @returns {boolean} Success status
- */
-function updateReadmeDefaultVersion(newVersion, readmeFile) {
-    try {
-        const content = fs.readFileSync(readmeFile, 'utf8');
-
-        // Update the default value in the options table
-        // Look for the pattern: | version | ... | string | X.Y.Z |
-        const readmeVersionRegex = /(\| version \| [^|]+ \| string \| )(\d+\.\d+\.\d+)( \|)/;
-        const updatedContent = content.replace(readmeVersionRegex, `$1${newVersion}$3`);
-
-        fs.writeFileSync(readmeFile, updatedContent);
-        return true;
-    } catch (error) {
-        throw new Error(`Could not update README file ${readmeFile}: ${error.message}`);
-    }
-}
-
-// === VERSION VALIDATION ===
-/**
- * Validates if a version string matches the expected format
- * @param {string} version - The version string to validate
- * @returns {boolean} True if valid, false otherwise
- */
-function validateVersionFormat(version) {
-    return VERSION_VALIDATION_REGEX.test(version);
-}
-
-/**
- * Validates that all required configuration files exist
- */
-function validateConfiguration() {
-    // Check if files exist
-    checkFileExists(YAML_FILE);
-    checkFileExists(JSON_FILE);
-    checkFileExists(README_FILE);
-
-    // Check if test files exist
-    for (const testFile of TEST_FILES) {
-        checkFileExists(testFile);
-    }
-}
-
-// === BUSINESS LOGIC ===
-
-/**
- * Gets the current default Ruby version from the JSON configuration file
- * @param {string} jsonFile - Path to the JSON configuration file
- * @returns {string} The current default version
- */
-function getCurrentDefaultVersion(jsonFile) {
-    try {
-        const data = readJsonFile(jsonFile);
-        return data.options.version.default;
-    } catch (error) {
-        throw new Error(`Could not read current default version: ${error.message}`);
-    }
-}
-
-/**
- * Checks if a version already exists in the YAML workflow file
- * @param {string} version - The version to check for
- * @param {string} yamlFile - Path to the YAML workflow file
- * @returns {boolean} True if version exists, false otherwise
- */
-function versionExistsInYaml(version, yamlFile) {
-    try {
-        const data = readYamlFile(yamlFile);
-        const versions = data.jobs.build.strategy.matrix.RUBY_VERSION || [];
-        return versions.includes(version);
-    } catch (error) {
-        throw new Error(`Could not check if version exists: ${error.message}`);
-    }
-}
-
-/**
- * Adds a new Ruby version to the YAML workflow file and sorts the versions
- * @param {string} newVersion - The new version to add
- * @param {string} yamlFile - Path to the YAML workflow file
- * @returns {boolean} Success status
- */
-function addVersionToYaml(newVersion, yamlFile) {
-    try {
-        // Read and parse the YAML file
-        const data = readYamlFile(yamlFile);
-
-        // Get current versions and add new one
-        const currentVersions = data.jobs.build.strategy.matrix.RUBY_VERSION || [];
-        const allVersions = [...new Set([...currentVersions, newVersion])];
-        const sortedVersions = allVersions.sort((a, b) => semver.rcompare(a, b));
-
-        // Update the data structure
-        data.jobs.build.strategy.matrix.RUBY_VERSION = sortedVersions;
-
-        // Write back to file
-        writeYamlFile(yamlFile, data);
-        return true;
-    } catch (error) {
-        throw new Error(`Could not update YAML file: ${error.message}`);
-    }
-}
-
-/**
- * Updates the default Ruby version in the JSON configuration file
- * @param {string} newVersion - The new default version
- * @param {string} jsonFile - Path to the JSON configuration file
- * @returns {boolean} Success status
- */
-function updateDefaultInJson(newVersion, jsonFile) {
-    try {
-        const data = readJsonFile(jsonFile);
-        data.options.version.default = newVersion;
-        writeJsonFile(jsonFile, data);
-        return true;
-    } catch (error) {
-        throw new Error(`Could not update JSON file: ${error.message}`);
-    }
-}
-
-/**
- * Increments the feature version in the JSON configuration file
- * @param {string} jsonFile - Path to the JSON configuration file
- * @returns {Object} Object containing oldVersion and newVersion
- */
-function bumpFeatureVersion(jsonFile) {
-    try {
-        const data = readJsonFile(jsonFile);
-
-        // Parse current version and increment patch version
-        const currentVersion = data.version;
-        const incrementedVersion = semver.inc(currentVersion, 'patch');
-
-        data.version = incrementedVersion;
-        writeJsonFile(jsonFile, data);
-
-        return {
-            oldVersion: currentVersion,
-            newVersion: incrementedVersion
-        };
-    } catch (error) {
-        throw new Error(`Could not bump feature version: ${error.message}`);
-    }
-}
-
-/**
- * Main function that orchestrates the Ruby version addition process
- */
-function main() {
-    // Check command line arguments
-    const args = process.argv.slice(2);
-
-    if (args.length !== 1) {
-        log('Usage: bin/add-ruby-version <ruby-version>', 'red');
-        log('Example: bin/add-ruby-version 3.4.5', 'yellow');
-        process.exit(1);
-    }
-
-    const newVersion = args[0];
-
-    // Validate version format
-    if (!validateVersionFormat(newVersion)) {
-        exitWithError('Invalid version format. Expected format: x.y.z (e.g., 3.4.5)');
-    }
-
-    // Validate configuration
-    validateConfiguration();
-
-    try {
-        // Check if version already exists
-        if (versionExistsInYaml(newVersion, YAML_FILE)) {
-            exitWithError(`Version ${newVersion} already exists in ${YAML_FILE}`);
-        }
-
-        log(`${emoji.search} Checking current configuration...`, 'cyan');
-
-        // Get current default version
-        const currentDefault = getCurrentDefaultVersion(JSON_FILE);
-        log(`Current default version: ${currentDefault}`);
-        log(`New version to add: ${newVersion}`);
-
-        // Add version to YAML file
-        log('');
-        log(`${emoji.edit} Adding ${newVersion} to ${YAML_FILE}...`, 'blue');
-        addVersionToYaml(newVersion, YAML_FILE);
-        log(`${emoji.check} Added to workflow matrix`, 'green');
-
-        // Check if new version should become the default
-        const comparisonResult = semver.compare(newVersion, currentDefault);
-        const filesModified = [YAML_FILE];
-
-        if (comparisonResult > 0) {
-            log('');
-            log(`${emoji.update} New version ${newVersion} is newer than current default ${currentDefault}`, 'yellow');
-            log(`Updating default version in ${JSON_FILE}...`);
-            updateDefaultInJson(newVersion, JSON_FILE);
-            log(`${emoji.check} Updated default version to ${newVersion}`, 'green');
-
-            // Update README with new default version
-            log(`Updating default version in ${README_FILE}...`);
-            updateReadmeDefaultVersion(newVersion, README_FILE);
-            log(`${emoji.check} Updated README default version to ${newVersion}`, 'green');
-
-            // Bump feature version when default changes
-            log('');
-            log(`${emoji.update} Bumping feature version...`, 'yellow');
-            const versionInfo = bumpFeatureVersion(JSON_FILE);
-            log(`${emoji.check} Feature version bumped from ${versionInfo.oldVersion} to ${versionInfo.newVersion}`, 'green');
-
-            filesModified.push(JSON_FILE, README_FILE);
-        } else {
-            log('');
-            log(`${emoji.info} New version ${newVersion} is not newer than current default ${currentDefault}`, 'cyan');
-            log('Default version remains unchanged');
-        }
-
-        // Update test files only if new version is newer than current default
-        log('');
-        let testFilesUpdated = 0;
-        if (comparisonResult > 0) {
-            log(`${emoji.edit} Updating test files...`, 'blue');
-            for (const testFile of TEST_FILES) {
-                updateVersionInTestFile(newVersion, testFile);
-                log(`${emoji.check} Updated ${testFile}`, 'green');
-                filesModified.push(testFile);
-                testFilesUpdated++;
-            }
-        } else {
-            log(`${emoji.info} Skipping test file updates (new version ${newVersion} is not newer than current default ${currentDefault})`, 'cyan');
-        }
-
-        // Success message
-        log('');
-        log(`${emoji.party} Successfully added Ruby version ${newVersion}!`, 'green');
-        log('');
-        log(`${emoji.file} Files modified:`, 'blue');
-        filesModified.forEach(file => {
-            log(`  • ${file}`);
-        });
-
-        log('');
-        log(`${emoji.bulb} Next steps:`, 'magenta');
-        log(`  1. Review the changes: git diff`);
-        log(`  2. Commit the changes: git add . && git commit -m 'Add Ruby ${newVersion}'`);
-        log(`  3. Push changes: git push`);
-
-    } catch (error) {
-        log(`${emoji.error} Error: ${error.message}`, 'red');
-        process.exit(1);
-    }
-}
-
-// Run the main function
-main();
+result = AddRubyVersion.call(ARGV[0], working_dir: Dir.pwd)
+exit(result[:success] ? 0 : 1)
diff --git a/lib/add_ruby_version.rb b/lib/add_ruby_version.rb
new file mode 100644
index 0000000..65bf48f
--- /dev/null
+++ b/lib/add_ruby_version.rb
@@ -0,0 +1,246 @@
+# frozen_string_literal: true
+
+require "json"
+require "fileutils"
+
+# Ruby Version Management Library
+#
+# This module automates the process of adding new Ruby versions to the devcontainer
+# configuration. It updates the versions JSON file, potentially updates the
+# default Ruby version, bumps the feature version, and updates test files.
+module AddRubyVersion
+  # Custom error class for version-related errors
+  class Error < StandardError; end
+
+  # File paths relative to the working directory
+  VERSIONS_JSON_FILE = ".github/ruby-versions.json"
+  FEATURE_JSON_FILE = "features/src/ruby/devcontainer-feature.json"
+  README_FILE = "features/src/ruby/README.md"
+  TEST_FILES = [
+    "features/test/ruby/test.sh",
+    "features/test/ruby/with_rbenv.sh"
+  ].freeze
+
+  # Version format pattern
+  VERSION_PATTERN = /\d+\.\d+\.\d+/
+  VERSION_EXACT_PATTERN = /\A#{VERSION_PATTERN}\z/
+
+  class << self
+    # Main entry point for adding a Ruby version
+    #
+    # @param version [String] The Ruby version to add (e.g., "3.4.0")
+    # @param working_dir [String] The directory to operate in
+    # @param output [IO] Output stream for messages (default: $stdout)
+    # @return [Hash] Result with :success, :files_modified, and :message keys
+    def call(version, working_dir:, output: $stdout)
+      runner = Runner.new(version, working_dir: working_dir, output: output)
+      runner.call
+    end
+  end
+
+  # Runner class that performs the actual version addition
+  class Runner
+    # ANSI color codes
+    COLORS = {
+      reset: "\e[0m",
+      green: "\e[32m",
+      blue: "\e[34m",
+      yellow: "\e[33m",
+      red: "\e[31m",
+      cyan: "\e[36m",
+      magenta: "\e[35m"
+    }.freeze
+
+    # Emoji helpers
+    EMOJI = {
+      search: "🔍",
+      edit: "📝",
+      check: "✅",
+      update: "🔄",
+      info: "ℹ️",
+      party: "🎉",
+      file: "📄",
+      bulb: "💡",
+      error: "❌"
+    }.freeze
+
+    attr_reader :version, :working_dir, :output
+
+    def initialize(version, working_dir:, output: $stdout)
+      @version = version
+      @working_dir = working_dir
+      @output = output
+    end
+
+    def call
+      validate_version_format!
+      validate_files_exist!
+      validate_version_not_duplicate!
+
+      files_modified = []
+
+      log("#{EMOJI[:search]} Checking current configuration...", :cyan)
+
+      current_default = current_default_version
+      log("Current default version: #{current_default}")
+      log("New version to add: #{version}")
+
+      # Add version to versions JSON file
+      log("")
+      log("#{EMOJI[:edit]} Adding #{version} to #{VERSIONS_JSON_FILE}...", :blue)
+      add_version_to_versions_file
+      log("#{EMOJI[:check]} Successfully added to #{VERSIONS_JSON_FILE}", :green)
+      files_modified << VERSIONS_JSON_FILE
+
+      # Check if new version should become the default
+      if version_newer?(version, current_default)
+        log("")
+        log("#{EMOJI[:update]} New version #{version} is newer than current default #{current_default}", :yellow)
+
+        update_default_version
+        log("#{EMOJI[:check]} Updated default version to #{version}", :green)
+
+        update_readme_default_version
+        log("#{EMOJI[:check]} Updated README default version to #{version}", :green)
+
+        log("")
+        log("#{EMOJI[:update]} Bumping feature version...", :yellow)
+        old_ver, new_ver = bump_feature_version
+        log("#{EMOJI[:check]} Feature version bumped from #{old_ver} to #{new_ver}", :green)
+
+        files_modified << FEATURE_JSON_FILE << README_FILE
+
+        log("")
+        log("#{EMOJI[:edit]} Updating test files...", :blue)
+        TEST_FILES.each do |test_file|
+          update_test_file(test_file)
+          log("#{EMOJI[:check]} Updated #{test_file}", :green)
+          files_modified << test_file
+        end
+      else
+        log("")
+        log("#{EMOJI[:info]} New version #{version} is not newer than current default #{current_default}", :cyan)
+        log("Default version remains unchanged")
+        log("")
+        log("#{EMOJI[:info]} Skipping test file updates (new version #{version} is not newer than current default #{current_default})", :cyan)
+      end
+
+      # Success message
+      log("")
+      log("#{EMOJI[:party]} Successfully added Ruby version #{version}!", :green)
+      log("")
+      log("#{EMOJI[:file]} Files modified:", :blue)
+      files_modified.each { |file| log("  • #{file}") }
+
+      log("")
+      log("#{EMOJI[:bulb]} Next steps:", :magenta)
+      log("  1. Review the changes: git diff")
+      log("  2. Commit the changes: git add . && git commit -m 'Add Ruby #{version}'")
+      log("  3. Push changes: git push")
+
+      { success: true, files_modified: files_modified }
+    rescue Error => e
+      log("#{EMOJI[:error]} Error: #{e.message}", :red)
+      { success: false, error: e.message }
+    end
+
+    private
+
+    def log(message, color = :reset)
+      output.puts "#{COLORS[color]}#{message}#{COLORS[:reset]}"
+    end
+
+    def path_for(relative_path)
+      File.join(working_dir, relative_path)
+    end
+
+    def validate_version_format!
+      unless version.match?(VERSION_EXACT_PATTERN)
+        raise Error, "Invalid version format. Expected format: x.y.z (e.g., 3.4.5)"
+      end
+    end
+
+    def validate_files_exist!
+      [VERSIONS_JSON_FILE, FEATURE_JSON_FILE, README_FILE, *TEST_FILES].each do |file|
+        unless File.exist?(path_for(file))
+          raise Error, "#{file} not found"
+        end
+      end
+    end
+
+    def validate_version_not_duplicate!
+      versions = read_json(VERSIONS_JSON_FILE)
+      if versions.include?(version)
+        raise Error, "Version #{version} already exists in #{VERSIONS_JSON_FILE}"
+      end
+    end
+
+    def read_json(relative_path)
+      JSON.parse(File.read(path_for(relative_path)))
+    end
+
+    def write_json(relative_path, data)
+      File.write(path_for(relative_path), JSON.pretty_generate(data) + "\n")
+    end
+
+    def current_default_version
+      data = read_json(FEATURE_JSON_FILE)
+      data.dig("options", "version", "default")
+    end
+
+    def version_newer?(new_version, current_version)
+      parse_version(new_version) > parse_version(current_version)
+    end
+
+    def parse_version(version_string)
+      Gem::Version.new(version_string)
+    end
+
+    def add_version_to_versions_file
+      versions = read_json(VERSIONS_JSON_FILE)
+      versions << version
+      versions.uniq!
+      versions.sort_by! { |v| Gem::Version.new(v) }.reverse!
+      write_json(VERSIONS_JSON_FILE, versions)
+    end
+
+    def update_default_version
+      data = read_json(FEATURE_JSON_FILE)
+      data["options"]["version"]["default"] = version
+      write_json(FEATURE_JSON_FILE, data)
+    end
+
+    def update_readme_default_version
+      path = path_for(README_FILE)
+      content = File.read(path)
+      # Update the default value in the options table
+      # Look for the pattern: | version | ... | string | X.Y.Z |
+      updated = content.gsub(/(\| version \| [^|]+ \| string \| )(\d+\.\d+\.\d+)( \|)/) do
+        "#{$1}#{version}#{$3}"
+      end
+      File.write(path, updated)
+    end
+
+    def bump_feature_version
+      data = read_json(FEATURE_JSON_FILE)
+      old_version = data["version"]
+      new_version = increment_patch_version(old_version)
+      data["version"] = new_version
+      write_json(FEATURE_JSON_FILE, data)
+      [old_version, new_version]
+    end
+
+    def increment_patch_version(version_string)
+      parts = version_string.split(".").map(&:to_i)
+      parts[2] += 1
+      parts.join(".")
+    end
+
+    def update_test_file(relative_path)
+      path = path_for(relative_path)
+      content = File.read(path)
+      updated = content.gsub(VERSION_PATTERN, version)
+      File.write(path, updated)
+    end
+  end
+end
diff --git a/test/add_ruby_version_test.rb b/test/add_ruby_version_test.rb
new file mode 100644
index 0000000..3571d5b
--- /dev/null
+++ b/test/add_ruby_version_test.rb
@@ -0,0 +1,391 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+require "minitest/autorun"
+require "fileutils"
+require "json"
+require "tempfile"
+require "stringio"
+require_relative "../lib/add_ruby_version"
+
+# Test suite for the add-ruby-version script
+#
+# These tests verify the behavior of the Ruby version management script,
+# which automates adding new Ruby versions to the devcontainer configuration.
+#
+# Run with: ruby test/add_ruby_version_test.rb
+# Or:       bundle exec ruby test/add_ruby_version_test.rb
+class AddRubyVersionTest < Minitest::Test
+  def setup
+    @temp_dir = Dir.mktmpdir("add-ruby-version-test")
+
+    # Create the directory structure
+    FileUtils.mkdir_p(File.join(@temp_dir, ".github"))
+    FileUtils.mkdir_p(File.join(@temp_dir, "features/src/ruby"))
+    FileUtils.mkdir_p(File.join(@temp_dir, "features/test/ruby"))
+  end
+
+  def teardown
+    FileUtils.rm_rf(@temp_dir)
+  end
+
+  def test_rejects_invalid_version_format_no_dots
+    setup_valid_environment
+    result = run_script("330")
+
+    refute result[:success], "Should fail for version without dots"
+    assert_match(/invalid version format/i, result[:output])
+  end
+
+  def test_rejects_invalid_version_format_two_parts
+    setup_valid_environment
+    result = run_script("3.3")
+
+    refute result[:success], "Should fail for version with only two parts"
+    assert_match(/invalid version format/i, result[:output])
+  end
+
+  def test_rejects_invalid_version_format_four_parts
+    setup_valid_environment
+    result = run_script("3.3.0.1")
+
+    refute result[:success], "Should fail for version with four parts"
+    assert_match(/invalid version format/i, result[:output])
+  end
+
+  def test_rejects_invalid_version_format_with_letters
+    setup_valid_environment
+    result = run_script("3.3.0-preview1")
+
+    refute result[:success], "Should fail for version with letters"
+    assert_match(/invalid version format/i, result[:output])
+  end
+
+  def test_accepts_valid_version_format
+    setup_valid_environment
+    result = run_script("3.4.0")
+
+    assert result[:success], "Should accept valid x.y.z format: #{result[:output]}"
+  end
+
+  def test_rejects_duplicate_version
+    setup_valid_environment(versions: ["3.3.0", "3.2.0"])
+    result = run_script("3.3.0")
+
+    refute result[:success], "Should fail when version already exists"
+    assert_match(/already exists/i, result[:output])
+  end
+
+  def test_accepts_new_version
+    setup_valid_environment(versions: ["3.3.0", "3.2.0"])
+    result = run_script("3.4.0")
+
+    assert result[:success], "Should accept new version: #{result[:output]}"
+  end
+
+  def test_adds_version_to_json_file
+    setup_valid_environment(versions: ["3.3.0", "3.2.0"])
+    run_script("3.4.0")
+
+    versions = read_versions_json
+    assert_includes versions, "3.4.0", "New version should be added to JSON"
+    assert_includes versions, "3.3.0", "Existing versions should be preserved"
+    assert_includes versions, "3.2.0", "Existing versions should be preserved"
+  end
+
+  def test_sorts_versions_descending
+    setup_valid_environment(versions: ["3.3.0", "3.2.0"])
+    run_script("3.4.0")
+
+    versions = read_versions_json
+    assert_equal ["3.4.0", "3.3.0", "3.2.0"], versions, "Versions should be sorted descending"
+  end
+
+  def test_sorts_versions_with_double_digit_patch
+    setup_valid_environment(versions: ["3.3.10", "3.3.9", "3.3.0"])
+    run_script("3.3.11")
+
+    versions = read_versions_json
+    assert_equal ["3.3.11", "3.3.10", "3.3.9", "3.3.0"], versions,
+      "Versions should be sorted correctly with double-digit patch numbers"
+  end
+
+  def test_adds_older_version_in_correct_position
+    setup_valid_environment(versions: ["3.3.0", "3.1.0"])
+    run_script("3.2.0")
+
+    versions = read_versions_json
+    assert_equal ["3.3.0", "3.2.0", "3.1.0"], versions,
+      "Older version should be inserted in correct sorted position"
+  end
+
+  def test_updates_default_when_version_is_newer
+    setup_valid_environment(versions: ["3.3.0", "3.2.0"], default_ruby: "3.3.0")
+    run_script("3.4.0")
+
+    feature = read_feature_json
+    assert_equal "3.4.0", feature["options"]["version"]["default"],
+      "Default should be updated to newer version"
+  end
+
+  def test_does_not_update_default_when_version_is_older
+    setup_valid_environment(versions: ["3.3.0", "3.2.0"], default_ruby: "3.3.0")
+    run_script("3.2.5")
+
+    feature = read_feature_json
+    assert_equal "3.3.0", feature["options"]["version"]["default"],
+      "Default should remain unchanged for older version"
+  end
+
+  def test_does_not_update_default_when_version_is_same_minor
+    setup_valid_environment(versions: ["3.3.0"], default_ruby: "3.3.0")
+    run_script("3.3.1")
+
+    feature = read_feature_json
+    assert_equal "3.3.1", feature["options"]["version"]["default"],
+      "Default should be updated for newer patch version"
+  end
+
+  def test_updates_readme_when_version_is_newer
+    setup_valid_environment(default_ruby: "3.3.0")
+    run_script("3.4.0")
+
+    readme = read_readme
+    assert_match(/\| string \| 3\.4\.0 \|/, readme,
+      "README should show new default version")
+    refute_match(/\| string \| 3\.3\.0 \|/, readme,
+      "README should not show old default version")
+  end
+
+  def test_does_not_update_readme_when_version_is_older
+    setup_valid_environment(default_ruby: "3.3.0")
+    run_script("3.2.5")
+
+    readme = read_readme
+    assert_match(/\| string \| 3\.3\.0 \|/, readme,
+      "README should keep old default version")
+  end
+
+  def test_bumps_feature_version_when_default_changes
+    setup_valid_environment(feature_version: "2.0.0", default_ruby: "3.3.0")
+    run_script("3.4.0")
+
+    feature = read_feature_json
+    assert_equal "2.0.1", feature["version"],
+      "Feature version should be bumped when default changes"
+  end
+
+  def test_does_not_bump_feature_version_when_default_unchanged
+    setup_valid_environment(feature_version: "2.0.0", default_ruby: "3.3.0")
+    run_script("3.2.5")
+
+    feature = read_feature_json
+    assert_equal "2.0.0", feature["version"],
+      "Feature version should not change when default is unchanged"
+  end
+
+  def test_bumps_feature_version_patch_correctly
+    setup_valid_environment(feature_version: "2.1.9", default_ruby: "3.3.0")
+    run_script("3.4.0")
+
+    feature = read_feature_json
+    assert_equal "2.1.10", feature["version"],
+      "Feature version patch should increment correctly"
+  end
+
+  def test_updates_test_files_when_default_changes
+    setup_valid_environment(default_ruby: "3.3.0")
+    run_script("3.4.0")
+
+    test_content = read_test_file("test.sh")
+    assert_match(/3\.4\.0/, test_content, "test.sh should contain new version")
+
+    rbenv_content = read_test_file("with_rbenv.sh")
+    assert_match(/3\.4\.0/, rbenv_content, "with_rbenv.sh should contain new version")
+  end
+
+  def test_does_not_update_test_files_when_default_unchanged
+    setup_valid_environment(default_ruby: "3.3.0")
+    run_script("3.2.5")
+
+    test_content = read_test_file("test.sh")
+    assert_match(/3\.3\.0/, test_content, "test.sh should keep old version")
+    refute_match(/3\.2\.5/, test_content, "test.sh should not contain older version")
+  end
+
+  def test_output_shows_success_message
+    setup_valid_environment
+    result = run_script("3.4.0")
+
+    assert_match(/successfully added/i, result[:output])
+    assert_match(/3\.4\.0/, result[:output])
+  end
+
+  def test_output_lists_modified_files
+    setup_valid_environment(default_ruby: "3.3.0")
+    result = run_script("3.4.0")
+
+    assert_match(/ruby-versions\.json/i, result[:output])
+    assert_match(/devcontainer-feature\.json/i, result[:output])
+    assert_match(/README\.md/i, result[:output])
+  end
+
+  def test_output_shows_version_comparison
+    setup_valid_environment(default_ruby: "3.3.0")
+    result = run_script("3.4.0")
+
+    assert_match(/current default.*3\.3\.0/i, result[:output])
+    assert_match(/new version.*3\.4\.0/i, result[:output])
+  end
+
+  def test_output_indicates_skipped_updates_for_older_version
+    setup_valid_environment(default_ruby: "3.3.0")
+    result = run_script("3.2.5")
+
+    assert_match(/not newer than current default/i, result[:output])
+    assert_match(/skipping/i, result[:output])
+  end
+
+  def test_fails_when_versions_json_missing
+    setup_valid_environment
+    FileUtils.rm(File.join(@temp_dir, ".github/ruby-versions.json"))
+    result = run_script("3.4.0")
+
+    refute result[:success], "Should fail when versions JSON is missing"
+    assert_match(/not found/i, result[:output])
+  end
+
+  def test_fails_when_feature_json_missing
+    setup_valid_environment
+    FileUtils.rm(File.join(@temp_dir, "features/src/ruby/devcontainer-feature.json"))
+    result = run_script("3.4.0")
+
+    refute result[:success], "Should fail when feature JSON is missing"
+    assert_match(/not found/i, result[:output])
+  end
+
+  def test_fails_when_readme_missing
+    setup_valid_environment
+    FileUtils.rm(File.join(@temp_dir, "features/src/ruby/README.md"))
+    result = run_script("3.4.0")
+
+    refute result[:success], "Should fail when README is missing"
+    assert_match(/not found/i, result[:output])
+  end
+
+  def test_fails_when_test_file_missing
+    setup_valid_environment
+    FileUtils.rm(File.join(@temp_dir, "features/test/ruby/test.sh"))
+    result = run_script("3.4.0")
+
+    refute result[:success], "Should fail when test file is missing"
+    assert_match(/not found/i, result[:output])
+  end
+
+  def test_handles_empty_versions_array
+    setup_valid_environment(versions: [])
+    result = run_script("3.4.0")
+
+    assert result[:success], "Should handle empty versions array: #{result[:output]}"
+    versions = read_versions_json
+    assert_equal ["3.4.0"], versions
+  end
+
+  def test_handles_major_version_change
+    setup_valid_environment(versions: ["3.3.0"], default_ruby: "3.3.0")
+    run_script("4.0.0")
+
+    feature = read_feature_json
+    assert_equal "4.0.0", feature["options"]["version"]["default"],
+      "Should handle major version upgrades"
+  end
+
+  def test_preserves_other_feature_json_fields
+    setup_valid_environment
+    run_script("3.4.0")
+
+    feature = read_feature_json
+    assert_equal "ruby", feature["id"], "Should preserve id field"
+    assert_equal "Ruby", feature["name"], "Should preserve name field"
+    assert_equal "Installs Ruby", feature["description"], "Should preserve description"
+  end
+
+  private
+
+  def create_versions_json(versions)
+    File.write(File.join(@temp_dir, ".github/ruby-versions.json"), JSON.pretty_generate(versions) + "\n")
+  end
+
+  def read_versions_json
+    JSON.parse(File.read(File.join(@temp_dir, ".github/ruby-versions.json")))
+  end
+
+  def create_feature_json(version: "2.0.0", default_ruby: "3.3.0")
+    data = {
+      "id" => "ruby",
+      "version" => version,
+      "name" => "Ruby",
+      "description" => "Installs Ruby",
+      "options" => {
+        "version" => {
+          "type" => "string",
+          "default" => default_ruby,
+          "description" => "The ruby version to be installed"
+        }
+      }
+    }
+    File.write(File.join(@temp_dir, "features/src/ruby/devcontainer-feature.json"), JSON.pretty_generate(data) + "\n")
+  end
+
+  def read_feature_json
+    JSON.parse(File.read(File.join(@temp_dir, "features/src/ruby/devcontainer-feature.json")))
+  end
+
+  def create_readme(default_version: "3.3.0")
+    content = <<~README
+      # Ruby
+
+      Installs Ruby and a version manager.
+
+      ## Options
+
+      | Options Id | Description | Type | Default Value |
+      |-----|-----|-----|-----|
+      | version | The version of ruby to be installed | string | #{default_version} |
+      | versionManager | The version manager to use | string | mise |
+    README
+    File.write(File.join(@temp_dir, "features/src/ruby/README.md"), content)
+  end
+
+  def read_readme
+    File.read(File.join(@temp_dir, "features/src/ruby/README.md"))
+  end
+
+  def create_test_file(filename, version: "3.3.0")
+    content = <<~BASH
+      #!/bin/bash
+      set -e
+      check "Ruby version is set to #{version}" bash -c "ruby -v | grep #{version}"
+      reportResults
+    BASH
+    File.write(File.join(@temp_dir, "features/test/ruby/#{filename}"), content)
+  end
+
+  def read_test_file(filename)
+    File.read(File.join(@temp_dir, "features/test/ruby/#{filename}"))
+  end
+
+  def run_script(version)
+    output = StringIO.new
+    result = AddRubyVersion.call(version, working_dir: @temp_dir, output: output)
+    { output: output.string, success: result[:success] }
+  end
+
+  def setup_valid_environment(versions: ["3.3.0", "3.2.0"], default_ruby: "3.3.0", feature_version: "2.0.0")
+    create_versions_json(versions)
+    create_feature_json(version: feature_version, default_ruby: default_ruby)
+    create_readme(default_version: default_ruby)
+    create_test_file("test.sh", version: default_ruby)
+    create_test_file("with_rbenv.sh", version: default_ruby)
+  end
+end